Question 11 Mark
What is a centripetal force?
Answer
View full question & answer→Force acting on a body which is in circular motion is called centripetal force. It acts towards the centre of the circular path.
Questions
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31 questions · timed · auto-graded
Question 21 Mark
Name the force required for circular motion. State its direction.
Answer
View full question & answer→Centripetal force is required for circular motion. It is always directed towards the centre of the circle.
Question 31 Mark
Give an example of motion in which speed remains uniform, but the velocity changes.
Answer
View full question & answer→The motion of a cyclist on a circular track is an example of motion in which speed remains uniform, but the velocity changes.
Question 41 Mark
Is it possible to have an accelerated motion with a constant speed? Name such type of motion.
Answer
View full question & answer→Yes, a uniform circular motion has an accelerated motion with a constant speed.
Question 51 Mark
Is centrifugal force a real force?
Answer
View full question & answer→No, centrifugal force is a fictitious force.
Question 61 Mark
Is centrifugal force the force of rection of centripetal force?
Answer
View full question & answer→No, centrifugal force is a fictitious force.
Question 71 Mark
With reference to the direction of action, how does a centripetal force differ from centrifugal force?
Answer
View full question & answer→They act in opposite directions.
Question 81 Mark
Where is the centre of gravity of a uniform ring situated?
Answer
View full question & answer→Centre of gravity of a uniform ring is situated at the centre of ring.
Question 91 Mark
At which point is the centre of gravity situated in a circular lamina?
Answer
View full question & answer→Centre of gravity of a circular lamina is situated at the centre of circular lamina.
Question 101 Mark
At which point is the centre of gravity situated in a triangular lamina.
Answer
View full question & answer→Centre of gravity of a triangular lamina is situated at the point of intersection of its medians
Question 111 Mark
What is the position of the centre of gravity of a cylinder?
Answer
View full question & answer→The position of the centre of gravity of cylinder is at the midpoint on the axis of cylinders.
Question 121 Mark
What is the position of the centre of gravity of a rectangular lamina?
Answer
View full question & answer→The position of the centre of gravity of a rectangular lamina is at the point of intersection of its diagonals
Question 131 Mark
Can the centre of gravity be situated outside the material of the body? Give an example
Answer
View full question & answer→Yes, the centre of gravity can be situated outside the material of the body. For example centre of gravity of ring.
Question 141 Mark
A uniform metre rule of mass 100g is balanced on a fulcrum at mark 40cm by suspending an unknown mass m at the mark 20cm.
To which side the rule will tilt if the mass m is moved to the mark 10cm ?
Answer
View full question & answer→The rule will tilt on the side of mass m (anticlockwise), if the mass m is moved to the mark 10cm.
Question 151 Mark
The diagram shows a uniform metre rule weighing 100gf, pivoted at its centre O. Two weights 150gf and 250gf hang from the point A and B respectively of the metre rule such that OA = 40 cm and OB = 20 cm.
Calculate :
The total clockwise moment about O
Calculate :
The total clockwise moment about O
Answer
View full question & answer→Total clockwise moment about O,
=250 gf x 20 cm= 5000 gf cm
Question 161 Mark
The diagram in the figure shows a uniform metre rule weighing 100 gf, pivoted as its centre O. two weight 150 gf and 250 gf hang from the point A and B respectively of the metre rule such that OA = 40 cm and OB = 20
cm .Calculate
The total anticlockwise moment about o.
Answer
View full question & answer→The total anticlockwise moment about O
= 150 gf x 40 cm = 6000 gf cm
Question 171 Mark
A physical balance has its arms of length 60 cm and 40 cm. What weight kept on pan of the longer arm will balance an object of weight 100 gf kept on other pan?
Answer
View full question & answer→From the principle of moments,
Anticlock moment $=$ Clockwise moment
$
100 gf \times 40 cm = W \times 60 cm
$
So weight on the longer pan.
$
W=\frac{100 gf \times 40 cm }{60 cm }=\frac{200 gf }{3}=66.67 gf
$
Anticlock moment $=$ Clockwise moment
$
100 gf \times 40 cm = W \times 60 cm
$
So weight on the longer pan.
$
W=\frac{100 gf \times 40 cm }{60 cm }=\frac{200 gf }{3}=66.67 gf
$
Question 181 Mark
Write the expression for the moment of force about a given axis.
Answer
View full question & answer→Moment of force about a given axis= Force x perpendicular distance of force from the axis of rotation.
Question 191 Mark
State whether the moment of force is a scalar or vector quantity?
Answer
View full question & answer→Moment of a force is a vector.
Question 201 Mark
Define moment of force and state its S.I unit.
Answer
View full question & answer→The moment of force is equal to the product of the magnitude of the force and the perpendicular distance of the line of action of force from the axis of rotation.
S.I. unit of moment of force is Newton metre (Nm).
Question 211 Mark
State the condition when a body is in static equilibrium. Give one example of static equilibrium.
Answer
View full question & answer→When a body remains in the state of rest under the influence of the applied forces, the body is in static equilibrium. For example, a book lying on a table is in static equilibrium.
Question 221 Mark
What do you mean by an equilibrium of a body?
Answer
View full question & answer→When a number of forces acting on a body produce no change in its state of rest or of motion, the body is said to be in equilibrium.
Question 231 Mark
State the couple effect. Give two example of couple action in our daily life.
Answer
View full question & answer→A couple is always needed to produce the rotation. For example turning a key in a lock and turning a steering wheel.
Question 241 Mark
What do you understand by the term couple?
Answer
View full question & answer→Two equal and opposite parallel forces not acting along the same line form a couple.
Question 251 Mark
A body is acted upon by two force of magnitude F, but in opposite directions. State the effect of the force if
the two forces act at two different points of the body at a separation r.
Answer
View full question & answer→The forces tend to rotate the body about the mid-point between two forces, Moment of forces= Fr
Question 261 Mark
A jack screw is provided with a long arm. Explain why?
Answer
View full question & answer→A jack screw has a long arm so that less effort is required to rotate it to raise or lower the jack, which is used to lift a heavy load like a vehicle.
Question 271 Mark
A spanner (or wrench) has a long handle. Why?
Answer
View full question & answer→A spanner (or wrench) has a long handle to produce larger turning moment so that nut can easily be turned with a less force.
Question 281 Mark
State the condition when on applying a force, the body has:
the rotational motion.
Answer
View full question & answer→When the body is pivoted at a point, it produces rotational motion.
Question 291 Mark
State the condition when on applying a force, the body has:
the translational motion
Answer
View full question & answer→When the body is free to move it produces translational motion.
Question 301 Mark
The stone of hand flour grinder is provided with a handle near its rim. Give reason.
Answer
View full question & answer→The stone of hand flour grinder is provided with a handle near its rim so that it can be rotated easily about the iron pivot at its centre by a small force applied at the handle.
Question 311 Mark
Why is it easier to open a door by applying the force at the free end of it?
Answer
View full question & answer→It is easier to open a door by applying the force at the free end of it because of the larger the perpendicular distance, less is the force needed to turn the body.