Assignment Questions for Class – IX PHYSICS
Contents
Pages
1. Motion
2
2. Force and Laws of Motion
3-5
3. Gravitation
6
Chapter 10-Motion
1.A man moved 6 m in south and then turned towards east to move 8 m. Calculate the distance
travelled by the man and the displacement .
2. A train travels 40 km at a uniform speed of 30 km h–1. Its average speed after travelling
another
40 km is 45 km h–1 for the whole journey. What will be speed in the second half of the
journey ?
3. A cyclist moving on a circular track of radius 40 m completes half a revolution in 40 sec.
What
is the average velocity of motion ?
4. A train, travelling at 72 km/hr is stopped in 4 seconds by the application of brakes. What is
the
retardation of the train ?
5. A moving train is brought to rest within 20 sec by applying brakes. Find the initial velocity, if
the retardation due to brakes is 2 m/s2.
6. A body moving along a straight line at 20m/s undergoes an acceleration of 4m/s2 After two
seconds what will be its speed . Also find the displacement.
7. The velocity time graph for an object is shown in the following figure.
State the kind of motion represented by OA, AB and BC
What is the velocity of the body at 4s and at 12s ?
Calculate the retardation of the body.
 Calculate the distance covered by the body (a) in the first 2 second (b) between 2 and 10 s. (c)
in the last 2 s.
8. The graph shows the position of body at different times. Calculate the speed of the body as it
moves from (i) A to B (ii) B to C and (iii) C to D
9. A car moving along a straight line at a speed of 90km/h stops in 10 seconds after the brakes
are
applied. (a) Find the acceleration, assuming it to be a constant. (b) Plot the graph of speed
versus
time.(b) Using graph, find the distance covered by the car after the brakes are applied.
10. A body is thrown upwards with some velocity.It returns to the same point after some
time. Draw its velocity -time graph.
11. Which physical quantity is denoted by the slope of velocity time graph?
12. During uniform circular motion which physical quantity of the body (i) remains constant
(ii) changes continuously.
13.Why is the motion of satellites around their planets considered an accelerated motion?
14. A body starts moving from rest with an acceleration of 4ms-2 . Find its velocity after 4 second
.
15. A train is moving with a speed of 20m/s. On switching off and applying brakes, it stops in 10
s.
Calculate the retardation and distance travelled in this time .
16. A body starts from rest and moves with an acceleration of 4ms-2 .
(a) In what time the body will acquire a speed of 80m/s ?
(b) How much distance will it travel in this time ?
17. A train starts from a station and moves with a constant acceleration for 2 minutes. If it
covers
a distance of 400m in this period , find the acceleration.
18. The minute hand of a clock is 7cm long. What is the distance and displacement of the
minute hand from 9:00 am to 9:30 am.Also calculate the speed of motion of minute hand.
19. A body travelling with a velocity of 60 ms-1 gains an acceleration of 100 ms-2. Calculate the
distance travelled by the body in 15 seconds .
20. A particle is pushed along a horizontal surface in such a way that it starts with a velocity of
12m/s. Its velocity decreases at a rate of 0.5m/s2 .(a) Find the time it will take to come to
rest.
(b) Find the distance covered by it before coming to rest.
21.An aeroplane lands at 432 km/hr and stops after covering a runaway of 4 km.Calculate (i)
acceleration (ii) time in which it comes to rest.
22 . A boy leaves his house at 9.30 A.M. for his school. The school is 2 km. away and classes
start at 10.00 A.M. If he walks at a speed of 3 km/h for the first km , at what speed should
he
walk the second km to reach just in time ?
23. Starting from rest, a cyclist moving at a uniform acceleration attains a velocity of 60m/s in
300 seconds. If he applies brake and slows down to rest at the rate of 2m/s2. Find
the acceleration in first 200 seconds
the time taken to come to rest in deceleration.
The displacement in the whole journey.
24. Is it possible for a body to have its velocity & acceleration pointing in opposite directions? If
Yes, give an example. If No, give reason why it is not possible? Plot the velocity-time
graph in
case the answer is Yes.
25. Consider this situation: A car moves with a velocity of 2 m/s for 10 seconds, and then its
velocity increases to 10m/s in the next 5 seconds. Thereafter its velocity decreases at a
uniform rate until it comes to rest after 10 seconds.
a. Express this entire run of the car on the velocity time graph.
b. From the graph identify the
i. time interval when the car was accelerating.
Displacement travelled while the car was decelerating.

Chapter 9-Force and Laws of Motion
How much force acts on a body whose momentum is constant ?
What is the principle behind the working of a rocket ?
When can a body stay at rest,even though forces act on it ?
Define the SI unit of force.
What is momentm ? Give its SI unit .
Why do not action and reaction cancel each other ?
Why does a gun recoil ?
Give reason for the following :
a) A person jumping out of a moving vehicle fall forward.
b) A gun recoils backward, when fired
c) Water sprinkler used for grass lawns begins to rotate as soon as the water is
ejected out of it.
d) A high jumper is often made to fall on a sand bed than to a concrete surface.
e) A cricketer often pulls his hands backward while catching a fast moving cricket ball.
f) Glass and porcelain articles are packed in straw or foam.
g) If someone jumps to the shore from a boat, the boat moves in opposite direction.
 A force of 5N gives a mass m1 an acceleration of 8m/s2 and a mass m2 an acceleration of
24m/s 2 . What acceleration would it give if both the masses are tied together ?
Which one requires more force- accelerating 10 g mass at 5m/s2 or a 20 g mass at 2m/s2 ?
A constant force acts on an object of mass 5 kg for a duration of 2s. It increases the object's
velocity from 3m/s to 7m/s. Find the magnitude of the applied force. Now if the force was
applied for a duration of 5s, what would be the final velocity of the object ?
A car initially at rest picks up a velocity of 72km/h in 20s.If the mass of the car is 1000kg,
Calculate the (a) Force developed by its engine. (b) distance covered by it in 20s
A cyclist and a person on a motor cycle are acted upon by the same force. If the acceleration
produced by the cyclist is 2/5 th that of motorcycle ,calculate the ration of masses of cyclist and
the person with motorcycle.
A 1000 kg mass having a speed of 10m/s is brought to rest over a distance of 100m.Find (a) the
retardation and (b) the retarding force.
A motorcycle is moving with a velocity of 90km/h and it takes 5s to stop after the brakes are
applied. Calculate the force exerted by the brakes on the motorcycle if its mass along with the
rider is 200 kg .
How much force is needed to produce an acceleration of 16cm/s2 in a body of mass 250 g ?
A body of mass 1kg is kept at rest. A constant force of 6 N starts acting on it. Find the time
taken by the body to move through a distance of 12 m.
A ship of mass 3 X10 7 kg initially at rest is pulled by a force of 5 X 10 4 N through a distance
of 3m. If the resistance due to water is negligible, then calculate the speed of the ship.
A player caught a cricket ball of mass 150 g moving at the rate of 20m/s .If he catches the ball
in 0.1 s, find the force of the blow exerted by the ball on the hands of the player.
A constant force of 12N acts on a body for 4s. Find the change in the linear momentum of the
body .
A force of 12N starts acting on a body kept at rest. Find the momentum of the body at 1s, 2s
and 5s after the force starts acting.
A block of mass 2500kg moving at 15m/s collides with a car of mass 1000 kg moving at 5m/s
in the opposite direction. With what velocity would the two move together?
A bullet of mass 15g leaves the barrel of a gun with a velocity of 120m/s.The gun recoils with a
velocity of 1m/s. Find the mass of the gun?
 A 5 kg rifle fires a 10g bullet at a velocity of 500m/s find the recoil velocity of the rifle?
A 6.5 kg shot is fired from a 2000 kg gun with a velocity of 30m/s. What is the recoil velocity
of the gun ?
A man throws a stone 0.5 kg vertically upward with a velocity of 20m/s Find (a) the initial
momentum (b) the momentum at the highest point (c) the retarding force .
An astronaut is drifting away from his spaceship. How can he return to his spaceship using only
an aerosol spray ?
If we release a ball from our hand, it starts moving . In order to keep the ball at rest ,we have to
apply a force on it by holding it. Explain why this is not a violation of Newton’s first law of
motion.
State Newton’s second law of motion. Write the mathematical expression of second law.
Deduce Newton's first law using the second law. State and prove the law of conservation of
momentum.
 Ram is playing with a ball and it strikes the floor. After striking the floor it bounces back
in the upward direction. Explain the reason of bouncing.
 The following is the distance-time table of an object in motion.
(a) What conclusion can be drawn about the velocity and acceleration of the object.
(b) What is the inference about the force acting on the object . Justify the answer.
Time (s)
0
1
2
3
4
5
6
Distance
0
96
120
180
205
310
420
(m)
Chapter 10-Gravitation
State Newton’s law of gravitation.
Derive the units of universal constant of gravitation G using formula of Newton's law of
gravitation.
According to Newton's law – every object exerts force of attraction on other object. Why do not
the bodies start moving towards each other?
Calculate the force of gravitation between the two bodies of mass 70 kg and 100kg kept at a
distance of 1km.
What is the value of 'G' at moon?
Define acceleration due to gravity. What do you mean by freefall?
What is the value of 'g' at the centre of the earth?
Explain why a 10 kg object will fall towards the earth with the same acceleration as a 1kg
object.
Show that the acceleration of a body falling towards the earth is independent of the mass of the
body.
Define weight of a body. How is it different from mass?
Why does weight of body become zero at the centre of earth?
Relate kg wt and Newton.
A man weighs 60 kgwt on earth. Find his mass and weight on the surface of moon.
What is the mass of an object whose weight is 98 N?
A stone is dropped from a height of 5m from the surface of the earth. Take g=10m/s2
(i) What will be its speed just before it hits the ground?
(ii) How much time would it take to reach the ground?
A
ball is thrown up with a speed of 20m/s. How high will it go before it begins to fall? Take
g=10m/s2
A ball is thrown vertically upward. It reaches maximum height of 19.6m. (i) What is the initial
speed of the ball? (ii) How much time is taken by the ball to reach the highest point?
The weight of any person on the moon is about 1/6 times that on the earth. He can lift a mass of
15kg on the earth. What will be the maximum mass, which can be lifted by the same force
applied by the person on the moon?
Identical packets are dropped from two aeroplanes, one above equator and the other above north
pole ,both at height h,assuming all conditions are identical, will those packets take same time to
reach the surface of earth. Justify your answer.