Question 11 Mark
lire relative density of mercury is $13.6.$ What does this statement mean$?$
AnswerThe relative density of mercury is $13.6,$ this means that mercury is $13.6$ times as heavy as an equal volume of water.
View full question & answer→Question 21 Mark
Name these force: The upward push of water on a submerged object.
Question 31 Mark
What is the other name of buoyant force?
AnswerUpthrust is the other name of buoyant force.
View full question & answer→Question 41 Mark
Name the force which makes heavy objects appear light when immersed in a liquid.
Question 51 Mark
What will be the weight of following objects on the earth when their weight on the moon is:
- $1800N$
- $400N$
Answer
- $1800N × 6 = 10800N$
- $400N × 6 = 2400N$
View full question & answer→Question 61 Mark
What is the weight of a $1$ kilogram mass on the earth? $\left(\mathrm{g}=9.8 \mathrm{~m} / \mathrm{s}^2\right)$.
AnswerWeight, $W=\mathrm{m} \times \mathrm{g} $
$1 \mathrm{~kg} \times 9.8 \mathrm{~m} / \mathrm{s}^2=9.8 \mathrm{~N}$
View full question & answer→Question 71 Mark
Name the scientist who gave he magnitude of buoyant force acting on a solid object immersed in a liquid.
AnswerArchimedes gave the magnitude of buoyant force acting on a solid object immersed in a liquid.
View full question & answer→Question 81 Mark
What is the value of relative density of water$?$
AnswerRelative density of water is $1.$
View full question & answer→Question 91 Mark
Explain why, if a stone held in our hand is released, it falls towards the earth.
AnswerThis is because the earth exerts a force of attraction (called gravity) on the stone and pulls it down.
View full question & answer→Question 101 Mark
What is the value of gravitational constant $G (i)$ on the earth, and $(ii)$ on the moon$?$
AnswerValue of gravitational constant $G$ on the earth and the moon is $=6.67 \times 10^{-11} \mathrm{Nm}^2 / \mathrm{kg}^2$
Note that the value of $G$ always remains constant irrespective of the location.
View full question & answer→Question 111 Mark
On what factor/factors does the weight of a body depend?
AnswerThe weight of a body is directly proportional to its mass. It also depends on the acceleration due to gravity which varies from place to place.
View full question & answer→Question 121 Mark
Why does ice float in water?
Answer The density of ice is less than that of water, so ice floats in water.
View full question & answer→Question 131 Mark
The gravitational force between two objects is $F.$ How will the force change when the distance between them is reduced to $\frac{1}{4}\text{th}$?
AnswerWe know, that the force of gravitation between two objects is inversely proportional to the square of distance between them. That is, $\text{F}\propto\frac{1}{\text{r}^2}$ Now when the distance between two objects is reduced to $\frac{1}{4}\text{th}$ that's is made $\frac{1}{4}$, then the force between them will become $16.$ i.e. $\bigg(\frac{1}{\frac{1}{4}}\bigg)^2$ $=16$
View full question & answer→Question 141 Mark
What name has been given to the force with which two objects lying apart attract each other?
AnswerGravitational force causes two objects lying apart attract each other.
View full question & answer→Question 151 Mark
State the units in which pressure is measured.
AnswerPressure is measured in newton per square meter $\left(\mathrm{N} / \mathrm{m}^2\right)$ i.e., Pascal $ ( Pa)$.
View full question & answer→Question 161 Mark
A stone resting on the ground has a gravitational force of $20\ N$ acting on it. What is the weight of the stone? What is its mass? $\left(\mathrm{g}=10 \mathrm{~m} / \mathrm{s}^2\right)$.
AnswerWeight of the stone $=$ Gravitational force acting on it $=20 \mathrm{~N}$ Weight, $\mathrm{W}=\mathrm{m} \times \mathrm{g} 20=\mathrm{m} \times 10 \mathrm{~m}=2 \mathrm{~kg}$
View full question & answer→Question 171 Mark
A body has a weight of 10kg on the surface of earth. What will be its weight when taken to the centre of the earth?
AnswerIts weight will be zero as value of g is zero at the centre of the earth.
View full question & answer→Question 181 Mark
On the earth, a stone is thrown from a height in a direction parallel to the earth’s surface while another stone is simultaneously dropped from the same height. Which stone would reach the ground first and why?
AnswerBoth stones will take the same time to reach the ground because the two stones fall from the same height.
View full question & answer→Question 191 Mark
Name the property of earth which is responsible for extremely small acceleration being produced in it as a result of attraction by other small objects.
AnswerExtremely large mass of the earth.
View full question & answer→Question 201 Mark
During a free fall, will heavier objects accelerate more than lighter ones?
AnswerNo, acceleration is independent of the mass of the body during free fall.
View full question & answer→Question 211 Mark
As the altitude of a body increases, do the weight and mass both vary?
AnswerWeight of the body varies with altitude; mass of an object is constant.
View full question & answer→Question 221 Mark
Why does a block of wood held under water rise to the surface when released?
AnswerBecause the weight of the block of wood is less than the weight of an equal volume of water. So when it is completely submerged in water, the upward buoyant force on it is greater than the downward gravitational force on it. Hence, the lock rises to the surface.
View full question & answer→Question 231 Mark
Which of the Kepler’s laws of planetary motion led Newton to establish the inverse-square rule for gravitational force between two bodies?
AnswerKepler’s third law of planetary motion led Newton to establish the inverse-square rule for gravitational force between two bodies.
View full question & answer→Question 241 Mark
When an object is dropped from a height, it accelerates and falls down. Name the force which accelerates the object.
AnswerGravitational force of the earth.
View full question & answer→Question 251 Mark
What is the usual value of the acceleration due to gravity of earth?
AnswerUsual value of acceleration due to gravity, $g=9.8 \mathrm{~m} / \mathrm{s}^2$.
View full question & answer→Question 261 Mark
Name these force: The force which wears away two surfaces as they move over one another.
Question 271 Mark
An object has mass of $20\ kg$ on earth. What will be its $(i)$ mass, and $(ii)$ weight, on the moon? $( g$ on moon $=1.6 \mathrm{~m} / \mathrm{s}^2).$
Answer
- Its mass will be $20\ kg$ as mass is a constant quantity.
- Weight, $W = m × g =20 × 1.6 = 32N.$
View full question & answer→Question 281 Mark
What is the relation between mass and weight of a body$?$
AnswerWeight, $W = m × g,$ i.e. the weight of a body is directly proportional to its mass.
View full question & answer→Question 291 Mark
What is the density of water in $SI$ units$?$
AnswerDensity of water $= 1000 \mathrm{~kg} / \mathrm{m}^3$.
View full question & answer→Question 301 Mark
Define mass of a body. What is the $SI$ unit of mass$?$
AnswerThe mass of a body is the quantity of matter contained in it. The SI unit of mass is kilogram $(kg).$
View full question & answer→Question 311 Mark
The weight of a body is $50N.$ What is its mass? $\left(\mathrm{g}=9.8 \mathrm{~m} / \mathrm{s}^2\right)$
AnswerWeight, $W = m × g.$
View full question & answer→Question 321 Mark
State the Kepler’s law which is represented by the relation $\text{r}^3\propto\text{T}^2.$
AnswerKepler’s law of periods states that: The cube of the mean distance of a planet from the sun is directly proportional to the square of time it takes to move around the sun.
View full question & answer→Question 331 Mark
Name the scientist who gave the three laws of planetary motion.
AnswerJohannes Kepler gave the three laws of planetary motion.
View full question & answer→Question 341 Mark
Define weight of a body. What is the $SI$ unit of weight$?$
AnswerThe weight of a body is the force with which it is attracted towards the centre of the earth. The $SI$ unit of weight is newton $(N).$
View full question & answer→Question 351 Mark
What do you mean by acceleration due to gravity$?$
AnswerWhen an object falls freely towards the surface of earth from a certain height, then its velocity changes. This change in velocity produces acceleration in the object which is known as acceleration due to gravity denoted the letter $g .$ The value of acceleration due to gravity is $\mathrm{g}=9.8 \mathrm{~m} / \mathrm{s}^2$.
View full question & answer→Question 361 Mark
A mug full of water appears light as long as it is under water in the bucket than when it is outside water. Why?
AnswerA mug full of water appears light as long as it is under water because buoyant force acts on it which reduces its effective weight and makes it appear lighter.
View full question & answer→Question 371 Mark
Does the acceleration produced in a freely falling body depend on the mass of the body?
AnswerNo, the acceleration produced in a freely falling body is independent of the mass of the body.
View full question & answer→Question 381 Mark
Which force is responsible for holding the solar system together?
AnswerGravitational force of the sun holds the solar system together.
View full question & answer→Question 391 Mark
State the value of universal gravitational constant. What was its value back in $1947?$
AnswerUniversal law of gravitation states that every object in the universe attracts every other object with a force which is proportional to the product of their masses and inversely proportional to the distance between them. universal gravitation constant $G = 6.673 × 10(-11)$
View full question & answer→Question 401 Mark
When a golf ball is lowered into a measuring cylinder containing water, the water level rises by $3cm^3$ when the ball is completely submerged. If the mass of ball in air is $33g$, find its density.
AnswerVolume of golf ball = rise in water level $= 30 cm^3$
Density of ball $=\frac{\text{Mass of ball}}{\text{Volume of ball}}=\frac{33}{30}=1.1\text{g}/\text{cm}^3$
View full question & answer→Question 411 Mark
What are fluids? Name two common fluids.
Answer Those substances which can flow easily are called fluids. All the liquid and gases are fluids, like water, air etc.
View full question & answer→Question 421 Mark
In which direction does the buoyant force on an object due to a liquid act?
AnswerBuoyant force on an object due to a liquid act s in the vertically upward direction.
View full question & answer→Question 431 Mark
Name the forces acting on an object while immersed in a liquid.
Answer The two forces acting on it are the gravitational force and the upthrust.
View full question & answer→Question 441 Mark
AnswerPressure is the force acting perpendicularly on a unit area of the object.
View full question & answer→Question 451 Mark
Give the formula for the gravitational force $F$ between two bodies of masses $M$ and $m$ kept at a distance d from each other.
AnswerThe gravitational force $F$ between two bodies of masses $M$ and $m$ kept at a distance $d$ from each other is: $\text{F}=\text{G}\times\frac{\text{m}\times\text{M}}{\text{d}^2}$ Here, gravitational constant, $G = 6.7 \times 10^{-11}Nm^2/kg^2$
View full question & answer→Question 461 Mark
Name the scientist who explained the motion of planets on the basis of gravitational force between the sun and planets.
AnswerNewton explained the motion of planets on the basis of gravitational force between the sun and planets.
View full question & answer→Question 471 Mark
Write down the weight of a $50\ kg$ mass on the earth. $\left(\mathrm{g}=9.8 \mathrm{~m} / \mathrm{s}^2\right)$.
AnswerWeight, $\mathrm{w}=\mathrm{m} \times \mathrm{g}=50 \times 9.8=490 \mathrm{~N}$
View full question & answer→Question 481 Mark
What name is given to ‘thrust per unit area’?
Answer Pressure is ‘thrust per unit area’.
View full question & answer→Question 491 Mark
Name these force: The force which pulled the apple off Isaac Newton’s tree.
Question 501 Mark
Which force is responsible for the moon revolving round the earth?
Answer Gravitational force is responsible for the moon revolving round the earth.
View full question & answer→Question 511 Mark
What causes buoyant force (or upthrust) on a boat?
AnswerThe buoyant force on a boat is caused by the pressure of water ‘pushing up’ on the bottom of the boat.
View full question & answer→Question 521 Mark
If the same body is taken to places having different gravitational field strength, then what will vary: its weight or mass?
AnswerIts weight varies; mass of an object is constant.
View full question & answer→Question 531 Mark
A car falls off a ledge and drops to the ground in $0.5$ seconds. Let $g = 10ms^{-2}$, then How high is the ledge from the ground?
AnswerHeight of the ledge would be equal to the distance travelled. And hence, height of the ledge = $1.25m$.
View full question & answer→Question 541 Mark
AnswerWeight is the force with which a body is attracted towards the center of the earth. It is directly proportional to the acceleration due to gravity. It is given by, Weight $=$ mass $×$ acceleration due to gravity
View full question & answer→Question 551 Mark
What is the acceleration produced in a freely falling body of mass $10\ kg? ($Neglect air resistance$)$
AnswerAcceleration produced in a freely falling body, irrespective of its mass, is $9.8 \mathrm{~m} / \mathrm{s}^2$
View full question & answer→Question 561 Mark
State the $SI$ unit of acceleration due to gravity.
Answer$SI$ unit of acceleration due to gravity is $m/s^2$.
View full question & answer→Question 571 Mark
The density of a body is $800 \mathrm{~kg} / \mathrm{m}^3$. Will it sink or float when dipped in a bucket of water$? ($Density of water $= \left.1000 \mathrm{~kg} / \mathrm{m}^3\right)$.
AnswerThe body will float when dipped in a bucket of water as its density is less than that of water.
View full question & answer→Question 581 Mark
If the mass of an object be $10\ kg ,$ what is its weight? $\left(\mathrm{g}=9.8 \mathrm{~m} / \mathrm{s}^2\right)$.
AnswerWeight, $W=m \times g=10 \times 9.8=98 \mathrm{~N}$
View full question & answer→Question 591 Mark
Name the quantity whose one of the units is Pascal $(Pa).$
AnswerPressure has unit of Pascal $(Pa).$
View full question & answer→Question 601 Mark
AnswerFree fall is the term that is used to describe a falling object that only has gravity acting upon it. Free falling objects accelerate at a rate of $9.8\ m/ s.$
View full question & answer→Question 611 Mark
If the weight of a body on the earth is $6\ N,$ what will it be on the moon$?$
AnswerWeight of the body on the surface of moon will be $1N$ approx. as the value of g on the surface of moon is one-sixth that of the earth.
View full question & answer→Question 621 Mark
Which is more fundamental, the mass of a body or its weight? Why?
AnswerThe mass of a body is more fundamental because mass of a body is constant and does not change from place to place.
View full question & answer→Question 631 Mark
What is the scientific name of the ‘upward force’ acting on an object immersed in a liquid?
AnswerBuoyant force or upthrust.
View full question & answer→Question 641 Mark
Write the common unit of density.
AnswerGrams per cubic centimeter $\left(\mathrm{g} / \mathrm{cm}^3\right)$.
View full question & answer→Question 651 Mark
AnswerThe upward force acting on an object immersed in a liquid is called upthrust.
View full question & answer→Question 661 Mark
What is the relation between pressure, force and area?
Answer$\text{Pressure}=\frac{\text{Force}}{\text{Area}}$
View full question & answer→Question 671 Mark
Name the source of centripetal force that the moon requires to revolve around the earth.
AnswerThe gravitational force is the source of the centripetal force that earth requires to revolve around the sun.
View full question & answer→Question 681 Mark
Name these force: The force which stops you falling through the floor.
Question 691 Mark
Name the principle which gives the magnitude of buoyant force acting on an object immersed in a liquid.
Question 701 Mark
What is the unit of relative density?
AnswerRelative density is a dimensionless quantity and has no unit the ratio of the density (mass of a unit volume) of a substance to the density of a given reference material. Specific gravity usually means relative density with respect to water.
View full question & answer→Question 711 Mark
What type of force is involved in the formation of tides in the sea?
Answer Gravitational force (exerted mainly by the moon and to some extent by the sun) is involved in the formation of tides in the sea.
View full question & answer→Question 721 Mark
An iron nail sinks in water but it floats in mercury. Why?
Answer An iron nail sinks in water but it floats in mercury because density of iron is more than that of water but less than that of mercury.
View full question & answer→Question 731 Mark
What is the acceleration of free fall?
AnswerAcceleration of free fall is the acceleration produced when a body falls under the influence of the force of gravitation of the earth alone. It is denoted by g and its value on the surface of the earth is $9.8 \mathrm{~m} \mathrm{~s}^{-2}$.
View full question & answer→Question 741 Mark
What force is responsible for the earth revolving round the sun?
AnswerGravitational force is responsible for the earth revolving round the sun.
View full question & answer→Question 751 Mark
What do you mean by buoyancy?
AnswerThe upward force exerted by any fluid (liquid, gas) on an object is known as upthrust or buoyancy.
View full question & answer→Question 761 Mark
What do you mean by free fall?
AnswerGravity of earth attracts every object towards its center. When an object is dropped from a certain height, it begins to fall towards Earth’s surface under the influence of gravitational force. Such a motion of object is called free fall.
View full question & answer→Question 771 Mark
What is the gravitational force between earth and an object called$?$
AnswerThe gravitational force between an earth and an object Weight and it is equal to product of mass$(m)$ and acceleration due to gravity$(g).$
View full question & answer→