Model Test Paper മാതൃകാ ചോദ്യപേപ്പർ
A full paper in the Kerala Class 9 Physics pattern for this chapter, covering the whole of “Laws of Motion”. Work on paper with a timer before you look at the solutions.
Standard IX · Physics
Chapter 3 · ചലനനിയമങ്ങൾ · Laws of Motion
- The first 15 minutes are cool-off time: read every question and plan your answers; do not write.
- Answer all questions. Marks for each question are shown on the right.
- For numericals write Given → Formula → Substitution → Answer with unit.
- Take the direction of motion (or the direction stated) as positive. Show the sign of forces and explain it.
SECTION AAnswer all · 8 × 1 = 8 marks
1.
The SI unit of momentum is .
(1)2.
Which one of the following is not a vector quantity?
(1)(a) force(b) momentum(c) speed(d) velocity
3.
In Galileo’s experiment, if there were no friction, a ball rolling on a horizontal surface would .
(1)4.
Passengers standing in a moving bus fall forward when the bus stops suddenly. This is due to .
(1)5.
The inertia of an object depends on its .
(1)6.
Find the relation and fill in: momentum : kg m/s :: impulse :
(1)7.
Forces of 30 N towards the east and 20 N towards the west act on a box at the same time. The resultant force is
(1)(a) 50 N east(b) 10 N east(c) 10 N west(d) zero
8.
Action and reaction forces act on (the same body / different bodies).
(1)SECTION BAnswer all · 5 × 2 = 10 marks
9.
State Newton’s first law of motion. Which two ideas are defined by this law?
(2)10.
A car of mass 1500 kg is moving with a velocity of 72 km/h. Calculate its momentum.
(2)11.
A force of 60 N acts on a trolley of mass 12 kg that is at rest. Find (a) the acceleration of the trolley (b) its velocity after 3 s.
(2)12.
While catching a fast cricket ball, a fielder pulls his hands backwards along with the ball. Why?
(2)13.
Give reasons: (a) When the branch of a mango tree is shaken, the mangoes fall. (b) When a person jumps from a small boat to the shore, the boat moves backwards.
(2)SECTION CAnswer all · 4 × 3 = 12 marks
14.
In the toy-car activity, a toy car on a plank is tied by strings to two pans hanging over pulleys at the two ends. Each pan holds 200 g. (a) Does the car move? Are the forces on it balanced or unbalanced? (b) 50 g more is placed on the left pan. What happens to the car? Why? (c) Are these forces internal or external forces for the car?
(3)15.
A football of mass 500 g lying on the ground is kicked. It leaves the foot with a velocity of 20 m/s. The foot was in contact with the ball for 0.05 s. Find (a) the change in momentum of the ball (b) the average force exerted on the ball (c) the impulse of the force.
(3)16.
Two identical spring balances A and B are hooked together. The free end of B is tied to a window bar and A is pulled with a force of 50 N. (a) What are the readings of A and B? (b) Which law of motion does this show? State the law. (c) Action and reaction are equal and opposite. Why don’t they cancel each other?
(3)17.
The velocity–time graph of a body of mass 2 kg is shown. Find the force acting on the body (a) from 0 to 4 s (b) from 4 s to 8 s (c) from 8 s to 10 s. What does the sign of the force in (c) tell you?
(3)SECTION DAnswer all · 2 × 5 = 10 marks
18.
A KSRTC bus of mass 10,000 kg (with passengers) is moving at 54 km/h. The driver applies the brakes and the bus stops uniformly in 5 s. (a) Find the initial momentum of the bus. (b) Find the braking force. What does its sign show? (c) Find the retardation and the distance the bus travels while stopping. (d) If the bus were moving at 108 km/h and stopped with the same retardation, how far would it go? (e) Why do standing passengers fall forward when the bus stops suddenly?
(5)19.
Two students A (40 kg) and B (60 kg) stand at rest on skates on a smooth (frictionless) floor. A pushes B with a force of 120 N for 0.5 s. (a) What force does B exert on A? (b) Find the acceleration of each student. (c) Find the velocity of each just after the push. (d) Find the momentum of each. What is the total momentum of the two after the push? (e) Which law explains why both move, and why does A move faster than B?
(5)