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Science M.C.Q. [I MARKS]

Friction · UP Board (UPMSP) STD 8 (UPMSP - English Medium). 221 questions.

Questions · Page 3 of 5

M.C.Q. [I MARKS]

MCQ 1011 Mark
What is the value of sliding friction for an object which requires $7\ N$ of force to move it from rest?
  • A
    $7\ N$
  • B
    Greater than $7\ N$
  • ✓
    Less than $7\ N$
  • D
    $14\ N$
Answer
Correct option: C.
Less than $7\ N$

Sliding friction is less than the friction that builds up before sliding, i.e., static friction. Hence, sliding friction is less than $7\ N.$

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MCQ 1021 Mark
A box is given a push across the floor. It comes to stop shortly after. Which one of the following reasons explain why this happen?
  • A
    Gravity is acting on the box in the direction opposite to the box's movement.
  • B
    Friction is acting on the box in the same direction of the box's movement.
  • ✓
    Friction is acting on the box in the direction opposite to the box's movement.
  • D
    The heat produced during the box's movement slows down the box.
Answer
Correct option: C.
Friction is acting on the box in the direction opposite to the box's movement.
When we push a box across the floor, force of friction comes into play in the direction opposite to the applied force and opposes the motion of the box. Hence, the box comes to stop shortly after.
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MCQ 1031 Mark
If the sliding friction between two surfaces is found to be 8N, then the static friction between these two surfaces is most likely to be:
  • A
    $5\ N.$
  • ✓
    $10N.$
  • C
    $4N.$
  • D
    $2N.$
Answer
Correct option: B.
$10N.$

The static friction is always greater than sliding friction.

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MCQ 1041 Mark
If the static friction between two surfaces $P$ and $Q$ is measured to be $50 N$, then the sliding friction between these two surfaces is most likely to be:
  • ✓
    $75N.$
  • B
    $45N.$
  • C
    $55N.$
  • D
    $65N.$
Answer
Correct option: A.
$75N.$

The static friction > Sliding Friction > Rolling friction.

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MCQ 1051 Mark
When friction is acting in the direction of $P$, in which direction do you think the force is applied?
  • A
    $P$
  • B
    $Q$
  • ✓
    $R$
  • D
    $S$
Answer
Correct option: C.
$R$

The force of friction acts opposite to the direction of applied force. Since, friction is acting along $P$, so the force must have been applied in the direction of $R.$

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MCQ 1061 Mark
Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play:
  • A
    Only if the objects are solid.
  • B
    Only if one of the two objects is liquid.
  • C
    Only if one of the two objects is gaseous.
  • ✓
    Irrespective of whether the objects are solid, liquid or gaseous.
Answer
Correct option: D.
Irrespective of whether the objects are solid, liquid or gaseous.
Force of friction acts in solids, liquids and gases and opposes the motion with respect to each other.
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MCQ 1071 Mark
Which of the following makes it difficult to quickly stop a ship moving in a sea by applying brakes?
  • ✓
    Low friction.
  • B
    Excess friction.
  • C
    High speed.
  • D
    External force.
Answer
Correct option: A.
Low friction.
Friction exerted by water is much less than that exerted by a solid. Hence, it takes more time to stop a ship in water.
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MCQ 1081 Mark
Friction has advantages as well as disadvantages. Dilip prepares a list of some of the advantageous applications of friction, as shown in the given table. Application of friction
$I$. Walking
$II.$ Writing
$III.$ Wearing out of shoes
$IV.$ Igniting a matchstick
$V.$ Gripping an object Which of the items listed in me given table is riot an advantage of friction?
  • A
    $II$
  • ✓
    $III$
  • C
    $IV$
  • D
    $V$
Answer
Correct option: B.
$III$

Friction plays an important role in life. Friction has disadvantages as well as advantages. One of the disadvantages of friction is the wearing out of shoes when used for a long time. The reason for this is the heat developed by friction between the shoes and the ground surface while walking.

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MCQ 1091 Mark
In which of the following cases the friction is helpful $(H)$ and troublesome $(T)?$
$a.$ Lighting a matchstick.
$b.$ Applying the brakes on a cycle.
$c.$ Use a towel to open tightly closed lid of a bottle.
$d.$ Pulling drawer out of a desk.
  • A
    $(a)-T, (b)-T, (c)-H, (d)-H$
  • B
    $(a)-T, (b)-T, (c)-H, (d)-H$
  • C
    $(a)-T, (b)-T, (c)-H, (d)-H$
  • ✓
    $(a)-T, (b)-T, (c)-H, (d)-H$
Answer
Correct option: D.
$(a)-T, (b)-T, (c)-H, (d)-H$
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MCQ 1101 Mark
The friction between two surfaces does not depend on one of the following. This one is:
  • ✓
    Amount of surface area of the two objects which is in contact with each other.
  • B
    Weight of the object which tends to move on the surface of other object.
  • C
    Degree of smoothness of surfaces of two objects in contact with each other.
  • D
    Degree of roughness of surfaces of two objects in contact with each other.
Answer
Correct option: A.
Amount of surface area of the two objects which is in contact with each other.
Friction does not depend on the area of contact.
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MCQ 1111 Mark
If the static friction between two surfaces $x$ and $y$ is found to be $20n$, then the rolling friction between these two surfaces should be most likely be:
  • A
    $25n$
  • B
    $20n$
  • ✓
    $5n$
  • D
    $50n$
Answer
Correct option: C.
$5n$
We know that friction force acts in an opposite direction to the direction in which an object moves. The maximum frictional force present between two objects is static friction. And sliding friction is smaller than static friction. And rolling friction is much less than sliding friction. The relationship between the three types of friction is: the static friction > sliding friction > rolling friction. Thus, the rolling friction will be less than $20n.$
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MCQ 1121 Mark
Which of the following statement is not true?
  • A
    Friction make the things slow down.
  • B
    Friction produces heat.
  • C
    Friction can stop the moving object.
  • ✓
    Friction is not useful.
Answer
Correct option: D.
Friction is not useful.
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MCQ 1131 Mark
Pappu is applying a large force in order to push a heavy box lying on the floor. Then, his younger brother, Chintu spreads a little bit of oil on the floor. Now, Pappu feels that it has become relatively easier to move the box. This happens because the.
  • A
    Oil magnifies the applied muscular force.
  • ✓
    Oil reduces the friction between two surfaces.
  • C
    Application of oil generates an upward thrust.
  • D
    Application of oil reduces the gravitational force.
Answer
Correct option: B.
Oil reduces the friction between two surfaces.
Oil is one of the best lubricants. The application of lubricants between two moving surfaces reduces the friction between them. Since friction always opposes motion, the resistance against the motion of the given box is reduced on the oil spread floor. Hence, Pappu can push the box by applying a relatively lesser muscular force.
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MCQ 1141 Mark
In which of the following activities is friction useful?
  • A
    Driving a car.
  • B
    Sitting on a chair.
  • C
    Rowing a boat.
  • ✓
    All of the above.
Answer
Correct option: D.
All of the above.
It will be difficult to sit on a chair without friction. In the other two cases too, friction is useful.
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MCQ 1151 Mark
In which of the following alternatives are the activities categorised correctly according to the advantages and disadvantages of the role of friction in them?
  • A
    Advantage of Friction Disadvantage of Friction
    Walking on a surface Writing on a blackboard
    Flying of an airplane Wearing out of a shoe
      Wearing out of a shoe
  • B
    Advantage of Friction Disadvantage of Friction
    Flying of an airplane Writing on a blackboard
    Wearing out of a shoe Applying brake on a moving car
      Walking on a surface
  • ✓
    Advantage of Friction Disadvantage of Friction
    Applying brake on a moving car Flying of an airplane
    Writing on a blackboard Wearing out of a shoe
    Walking on a surface  
  • D
    Advantage of Friction Disadvantage of Friction
    Applying brake on a moving car Flying of an airplane
    Writing on a blackboard Walking on a surface
    Wearing out of a shoe  
Answer
Correct option: C.
Advantage of Friction Disadvantage of Friction
Applying brake on a moving car Flying of an airplane
Writing on a blackboard Wearing out of a shoe
Walking on a surface  
When breaks are applied on a moving car, the break pads come in contact with the wheels and reduce the speed of the wheels due to friction between the pads and tyres. As a result, the frictional force, which acts in between the road and tyres of the car, also increases and the car stops. Without friction, it would be impossible to stop a car after starting. Therefore, this is an advantage of friction. The surface of a blackboard is made rough in order to write on it. Writing with chalk on blackboard is easy because of the friction that exists in between the tip of the chalk and the blackboard. This friction results in the deposition of chalk on the blackboard. It would not be possible to write if the blackboard is made frictionless. Therefore, this is an advantage of the force of friction. It is the friction between the foot and the road that helps us in walking. If there was no friction present there, then we would not be able to walk on the road. This is the advantage of friction. Disadvantages of friction: Sole of a shoe wears out because of heat produced by the friction. Hence, it is a disadvantage of friction. During flight, the frictional force between an airplane body and air opposes the motion of the airplane. Therefore, more energy of airplane engine is spent to overcome the resistance offered by the air friction and the speed of the airplane decreases. Therefore, this is a disadvantage of friction.
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MCQ 1161 Mark
Fluid friction do not depend on:
  • A
    Speed of object
  • B
    Shape of object
  • C
    Nature of the fluid
  • ✓
    Speed of the fluid
Answer
Correct option: D.
Speed of the fluid
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MCQ 1171 Mark
In which of the following cases is friction desirable?
  • ✓
    Movement of piston in a cylinder.
  • B
    A vehicle speeding.
  • C
    Running on a track.
  • D
    All of the above.
Answer
Correct option: A.
Movement of piston in a cylinder.
Friction is desirable to stop or reduce speed of a speeding vehicle. When the brakes are applied in a speeding vehicle, they rub against the wheels in motion. Due to the friction between the brakes and wheels, the speed of vehicle is reduced or it may come to stop.
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MCQ 1181 Mark
In a large commercial complex, there are four ways to reach the main road. One of the path has loose soil, the second is laid with polished marble, the third is laid with bricks and the fourth has gravel surface. It is raining heavily and paheli wishes to reach the main road. The path on which she is least likely to slip is:
  • A
    Loose soil.
  • B
    Polished marble.
  • C
    Bricks.
  • ✓
    Gravel.
Answer
Correct option: D.
Gravel.
She should use gravel surface path because only in this path. She will have sufficient friction force to walk easily.
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MCQ 1191 Mark
The designing of Cars has improved over the years. These days, cars are designed to be more aerodynamic. Cars are designed to be more aerodynamic in order to.
  • ✓
    Increase their speed.
  • B
    Make them attractive.
  • C
    Make them less polluting.
  • D
    Increase the space inside them.
Answer
Correct option: A.
Increase their speed.
Cars are designed to be more aerodynamic in order to increase their speed by reducing the air resistance acting on them.
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MCQ 1201 Mark
A box is placed on three different surfaces "a marble floor, a cardboard sheet, and a sandpaper. The minimum forces required to simply move the box on the surfaces are $F_m,F_c,$ and $F_s$ respectively. The three forces can be arranged in the decreasing order as.
  • A
    $F_C< F_M < F_s$
  • B
    $F_C< F_S < F_M$
  • ✓
    $F_M < F_C < F_S$
  • D
    $F_S < F_C < F_S$
Answer
Correct option: C.
$F_M < F_C < F_S$
When a body that is resting on a surface is moved along the surface, a static friction is generated between the two contact surfaces. The minimum force required to simply move the body is equal to the magnitude of the generated static friction. The static friction offered by a marble floor is less than that offered by a cardboard sheet and sandpaper. Again, the static friction offered by a cardboard sheet is less than that offered by a sandpaper. Hence, the minimum.
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MCQ 1211 Mark
Four cubical boxes, made up of the same material, are placed on the ground and are pushed with a constant force $d_1, d_2, d_3$ and $d_4$ are the distances travelled by the boxes. They are related as $d_3 > d_2 > d_4 > d_1$ The sides $a_1, a_2, a_3$ and $a_4$ of the respective boxes are related as.
  • A
    $a_1 > a_2 > a_3 > a_4$
  • ✓
    $a_1 > a_4 > a_2 > a_3$
  • C
    $a_3 > a_2 > a_4 > a_1$
  • D
    $a_4 > a_3 > a_2 > a_1$
Answer
Correct option: B.
$a_1 > a_4 > a_2 > a_3$
The motion of the boxes on the ground is opposed by the friction offered by the irregularities present on the surface. The magnitude of friction depends on the mass of the moving object. The greater the mass of the moving object, the more is the friction and vice$-$versa. Here all the boxes are cubical in shape and made up of the same material. Therefore, the friction of each box will depend on its volume, which is proportional to its mass. It is given that the distances are related as $d_3 >d_2>d_4 >d_1$ Hence, it can be inferred that the frictions offered by the ground to the boxes are related as: Friction on box $1 >$ Friction on box $4 >$ Friction on box $2 >$ Friction on box $3$ Hence, the masses, i.e., the volumes in this case are related as: Mass of box $1 >$ Mass of box $4 >$ Mass of box $2 >$ Mass of box $3$
$\therefore$ the sides of the boxes are related as: $a_1 > a_4 > a_2 > a_3$
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MCQ 1221 Mark
A big wooden box is being pushed on the ground from east to west direction. The force of friction due to ground will act on this box towards:
  • A
    North direction.
  • B
    South direction.
  • C
    East direction.
  • ✓
    West direction.
Answer
Correct option: D.
West direction.
The force of friction acts opposite to the direction of motion.
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MCQ 1231 Mark
It is difficult to walk on an oily floor because.
  • A
    Floor gets spoiled.
  • B
    There is more resistance.
  • C
    Force of friction is high.
  • ✓
    Force of friction is very less.
Answer
Correct option: D.
Force of friction is very less.
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MCQ 1241 Mark
Lubricants are used to increase the efficiency and reduce the wear and tear of machines. The application of lubricants between machine parts helps to.
  • ✓
    Reduce friction.
  • B
    Develop more heat.
  • C
    Increase gravitational force.
  • D
    Change atmospheric pressure.
Answer
Correct option: A.
Reduce friction.
Lubricants are thick, oily liquids. They cause two surfaces to easily slip on one another. This is because they reduce the friction between the two surfaces by creating a smooth layer between them. When lubricants are applied between two machine parts that are moving in contact with each other, the friction between them is reduced. This helps the machine parts to move faster without much wear and tear, thereby enhancing the efficiency of the machine.
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MCQ 1251 Mark
Why does a meteor burn upon entering the earth's atmosphere?
  • A
    Due to gravitational pull.
  • B
    Due to the heat of the earth.
  • C
    Due to solar radiation.
  • ✓
    Due to excess friction in air.
Answer
Correct option: D.
Due to excess friction in air.
Due to the very high speed of meteor when it enters the earth's atmosphere, the heat produced by the friction of air is very large which causes the meteor to burn.
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MCQ 1261 Mark
Do you want to increase or decrease friction when riding a bicycle?
  • A
    Increase.
  • ✓
    Both.
  • C
    Decrease.
  • D
    None of these.
Answer
Correct option: B.
Both.
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MCQ 1271 Mark
Which force prevents us from slipping while walking on the road?
  • A
    Muscular force of our body.
  • B
    Gravitational pull by the earth.
  • ✓
    Frictional force.
  • D
    Balanced forces of nature.
Answer
Correct option: C.
Frictional force.
When we push the ground with our feet, the friction provides a forward reaction to our push and makes us move forward. $($Walking on slippery ground is difficult because the frictional force is not enough to prevent slipping$).$
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MCQ 1281 Mark
Which of the following is reduced by the correct measure of air pressure in the tyres?
  • A
    Static friction.
  • B
    Sliding friction.
  • ✓
    Rolling friction.
  • D
    All of the above.
Answer
Correct option: C.
Rolling friction.
The correct measure of air pressure in the tyres provides an air cushion to reduce rolling friction.
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MCQ 1291 Mark
Airplanes are designed in a particular shape called the streamline shape. The streamline design reduces the.
  • A
    Speed of the plane.
  • B
    Weight of the plane.
  • C
    The cost of production.
  • ✓
    Heat generated by air friction.
Answer
Correct option: D.
Heat generated by air friction.
The shape of an airplane is made streamlined to reduce air friction. The streamlined shape allows the easy passage of air. Therefore, the heat generated by air friction becomes less.
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MCQ 1301 Mark
Arpita observes that the match stick is not catching fire even when she is rubbing it gently against the comer of the matchbox. The match box had been used many times before also. The possible reason for the given problem is that the.
  • A
    Matchbox has lost its chemical.
  • ✓
    Matchbox has lost its roughness.
  • C
    Quality of wood used in the match stick is not good.
  • D
    Quality of chemical used in the match stick is not good.
Answer
Correct option: B.
Matchbox has lost its roughness.
Working of a match stick is based on the fact that heat is generated when two surfaces are rubbed against each other. Heat is generated by the friction caused between the matchbox and the stick. The given matchbox is very old. It has been used many times previously. Therefore, it can be concluded that the matchbox has lost its roughness. Hence, the required friction is not generated to ignite the stick.
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MCQ 1311 Mark
What kind of substances are known as lubricants.
  • A
    Increase friction
  • ✓
    Decrease friction
  • C
    Increase or decrease friction
  • D
    None of these
Answer
Correct option: B.
Decrease friction
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MCQ 1321 Mark
There are three types of friction, namely sliding, static, and rolling. They are respectively denoted as $f _{\text {sl, }} f _{\text {st }}$ and $f _{\text {roll }}$. On a given surface, the given frictional forces are related as.
  • A
    $F_{\text {sl }}>F_{\text {st }}>F_{\text {roll }}$
  • ✓
    $F_{\text {st }}>F_{\text {sl }}>F_{\text {roll }}$
  • C
    $F_{\text {st }}>F_{\text {roll }}>F_{\text {sl }}$
  • D
    $F_{\text {st }}>F_{\text {roll }}>F_{\text {st }}$
Answer
Correct option: B.
$F_{\text {st }}>F_{\text {sl }}>F_{\text {roll }}$
B.  $F_{\text {st }}>F_{\text {sl }}>F_{\text {roll }}$
Explanation:
The force of friction present between any two given objects depends on the nature of the motion of one over the other. Friction is offered by the interlocking of surfaces. When two surfaces are at rest over one another, the interlocking is the maximum. This is called static friction. Maximum force is required to overcome static friction $\left(f_{s t}\right)$. Sliding friction, $f_{s l}$, is greater than rolling friction, $f_{\text {roll }}$. This is because it is more difficult to slide over interlocking than roll them over. Hence, these frictions are related as: $f_{s t}>f_{s l}>f_{\text {roll }}$.
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MCQ 1331 Mark
Sliding friction is $............$ than/ to rolling friction.
  • ✓
    Smaller
  • B
    Greater
  • C
    Equal
  • D
    None of the above
Answer
Correct option: A.
Smaller
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MCQ 1341 Mark
A body of weight $50\ N$ is placed on a smooth surface. If the force required to move the body on the surface is $30\ N$ the coefficient of friction is.
  • ✓
    $0.60$
  • B
    $1.2$
  • C
    $0.3$
  • D
    $1.67$
Answer
Correct option: A.
$0.60$

The force of friction on a body sliding on a horizontal surface is, $F = m$ mg Given,
$\text{F}=30\text{N},\ \text{mg}=50\text{N}$
$\mu=\frac{\text{F}}{\text{mg}}=\frac{30}{50}=0.6$

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MCQ 1351 Mark
In a large commercial complex there are four ways to reach the main road. One of the path has loose soil, the second is laid with polished marble, the third is laid with bricks and the fourth has gravel surface. It is raining heavily and Paheli wishes to reach the main road. The path on which she is least likely to slip is:
  • A
    Loose soil.
  • B
    Bricks.
  • C
    Polished marble.
  • ✓
    Gravel.
Answer
Correct option: D.
Gravel.
She should use gravel surface path because only in this path. She will have sufficient friction force to walk easily.
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MCQ 1361 Mark
A spring balance can be used to measure:
  • A
    Mass of an object and force acting on an object.
  • B
    Force acting on an object and density of an object.
  • ✓
    Force acting on an object and weight of an object.
  • D
    Weight of an object.
Answer
Correct option: C.
Force acting on an object and weight of an object.
The spring balance is a device which is used for measuring force acting on an object. The spring balance contain a coiled spring which gets stretched when a force is applied to its free end or hook end. When the spring balance is held vertically, it is said to measure the weight of an object hung from its hook, because weight of an object is also a force. Therefore, a spring balance is a device, used to measure force acting on an object and weight of an object.
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MCQ 1381 Mark
Which of the following statements is incorrect?
  • A
    Friction acts on a ball rolling along the ground.
  • B
    Friction acts on a boat moving on water.
  • C
    Friction acts on a bicycle moving on a smooth road.
  • ✓
    Friction does not act on a ball moving through air.
Answer
Correct option: D.
Friction does not act on a ball moving through air.
Friction will act in case of ball moving through air always.
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MCQ 1391 Mark
In figure, a boy is shows pushing the box from right to left. The force of friction will act on the box:
  • A
    From right to left (←)
  • ✓
    Vertically downwards (→)
  • C
    Vrom left to right (↓)
  • D
    Vertically upwards (↑)
Answer
Correct option: B.
Vertically downwards (→)

The force of friction will be from left to right $(-4)$ because the friction force always acts in opposite direction to the motion.

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MCQ 1401 Mark
The sole of the shoes becomes plain after wearing it for several months. The reason is.
  • ✓
    Wearing out due to friction.
  • B
    Wearing out due to no friction.
  • C
    Sole is of bad quality.
  • D
    None of the above.
Answer
Correct option: A.
Wearing out due to friction.
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MCQ 1411 Mark
Ram and Shyam are pushing two identical boxes. Ram is pushing box $I$ that is placed on a wheel cart, while Shyam is pushing box $II$ that is placed on the ground. Both Ram and Shyam are trying to maintain a steady motion of the boxes. It is relatively difficult for Shyam to maintain a steady motion of box $II$ because.
  • ✓
    Sliding friction is greater than rolling friction.
  • B
    Rolling friction is greater than sliding friction.
  • C
    Static friction is greater than sliding friction.
  • D
    Sliding friction is greater than static friction.
Answer
Correct option: A.
Sliding friction is greater than rolling friction.

Sliding friction is always greater than rolling friction. Box $II$ is sliding on the ground because of the force applied by Shyam. Box $I$ is rolling on wheels because of the force applied by Ram. Hence, Shyam has to apply a greater force to maintain a steady motion of his box.

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MCQ 1421 Mark
Lubricant:
  • ✓
    Reduce friction.
  • B
    Increase friction.
  • C
    Both $(A)$ and $(B)$
  • D
    None of these.
Answer
Correct option: A.
Reduce friction.
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MCQ 1431 Mark
Anoop and Sohail while studying about friction decided to perform an experiment. They placed equal masses of an ice block and sand paper block on an inclined plastic tray as shown below.
What happens when both the blocks start moving?
  • ✓
    Ice block reaches the bottom of the tray first.
  • B
    Sand paper block reaches the bottom of the tray first.
  • C
    Both the blocks reach the bottom of the tray at the same time.
  • D
    Both the blocks offer the same amount of friction.
Answer
Correct option: A.
Ice block reaches the bottom of the tray first.
As both the blocks have the same mass, the friction depending on the weight of the blocks is the same and does not affect friction. Friction depends on the nature of the surfaces and sand paper is rougher than the ice block. Ice block offers the least friction than sand paper block. Hence, ice block reaches the bottom of the tray first.
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MCQ 1441 Mark
When does a body have zero force of friction?
  • ✓
    When no force is applied on a body at rest.
  • B
    When a large force is applied on a body.
  • C
    When a body is rolling on the surface.
  • D
    When a body is sliding on the surface.
Answer
Correct option: A.
When no force is applied on a body at rest.
Friction is the relative motion between two surfaces in contact. So, a body has zero force of friction when it is at rest, i.e. when no force is applied on it.
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MCQ 1451 Mark
Which friction of the following is the highest?
  • A
    Sliding friction.
  • B
    Rolling friction
  • ✓
    Static friction
  • D
    None of these
Answer
Correct option: C.
Static friction
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MCQ 1461 Mark
A box was pushed equal distance on four different surfaces. The force needed for each surface was recorded in the given table.
Surface
$M$
$N$
$O$
$P$
Force Needed (N)
$670$
$570$
$320$
$500$
On which surface was the friction least?
  • A
    $M$
  • B
    $N$
  • ✓
    $O$
  • D
    $P$
Answer
Correct option: C.
$O$

Friction opposes the motion of an object. For surface $O$, force needed to push the box is least i.e., $320N$, so it has least friction.

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MCQ 1471 Mark
The joints of Latifs garage door are producing sound. To solve this problem, he must apply.
  • A
    Saw dust in the joints of the door.
  • B
    Water in the joints of the door.
  • C
    Sand in the joints of the door.
  • ✓
    Oil in the joints of the door.
Answer
Correct option: D.
Oil in the joints of the door.
The joints of the door are producing sound because of an increase in friction between the two surfaces. To reduce this, he must apply oil between the joints of the door. Application of oil helps in reducing surface irregularities and hence, reduces friction. This is because oil is a very good lubricating agent.
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MCQ 1481 Mark
A spring balance can be used to measure:
$A.$ Mass of an object.
$B.$ Force acting on an object.
$C.$ Density of an object.
$D.$ Weight of an object.
  • A
    $A$ and $B$
  • B
    $B$ and $C$
  • ✓
    $B$ and $D$
  • D
    Only $D$
Answer
Correct option: C.
$B$ and $D$
A spring balance can measure both the force acting on it as well as the weight of the object.
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MCQ 1491 Mark
How can friction be decreased?
  • ✓
    By using smooth surfaces.
  • B
    By using dry surfaces.
  • C
    By increasing the weight of the body.
  • D
    All of the above.
Answer
Correct option: A.
By using smooth surfaces.
Friction can be decreased by making the surfaces smooth.
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MCQ 1501 Mark
Lubricants are substances which.
  • A
    Increase friction.
  • B
    Are used to light fire.
  • ✓
    Reduce friction.
  • D
    Are used to put out a fire.
Answer
Correct option: C.
Reduce friction.
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