30 MCQ Questions for Class 9 Science: Chapter 8 Force and Laws of Motion
Question 1. What is the unit of force in the SI system?
a) Kilogram
b) Newton
c) Meter
d) Second
Answer:
b) Newton
Question 2. Which law of motion gives the measure of force?
a) First law of motion
b) Second law of motion
c) Third law of motion
d) Law of gravitation
Answer:
b) Second law of motion
Question 3. The tendency of objects to resist a change in their state of rest or of uniform motion is called:
a) Momentum
b) Inertia
c) Acceleration
d) Friction
Answer:
b) Inertia
Question 4. According to the third law of motion, action and reaction:
a) Always act on the same object
b) Always act on different objects
c) Are always equal and opposite
d) Both b and c
Answer:
d) Both b and c
Question 5. The momentum of an object is the product of its:
a) Mass and velocity
b) Mass and acceleration
c) Force and displacement
d) Energy and mass
Answer:
a) Mass and velocity
Question 6. What causes a change in the state of motion of an object?
a) Balanced force
b) Unbalanced force
c) Frictional force
d) Gravitational force
Answer:
b) Unbalanced force
Question 7. An object of mass ‘m’ is moving with a velocity ‘v’. Its momentum is given by:
a) mv²
b) ½ mv²
c) mv
d) ½ mv
Answer:
c) mv
Question 8. The inertia of an object tends to cause the object:
a) To increase its speed
b) To decrease its speed
c) To resist any change in its state of motion
d) To move in a circular path
Answer:
c) To resist any change in its state of motion
Question 9. When a carpet is beaten with a stick, dust comes out of it. This is an example of:
a) Newton’s first law of motion
b) Newton’s second law of motion
c) Newton’s third law of motion
d) Law of conservation of momentum
Answer:
a) Newton’s first law of motion
Question 10. If the mass of an object is 6 kg and it is moving with a velocity of 2 m/s, its momentum will be:
a) 12 kg m/s
b) 3 kg m/s
c) 8 kg m/s
d) 4 kg m/s
Answer:
a) 12 kg m/s
Question 11. According to the third law of motion, when we push on an object:
a) The object moves in the direction of the force
b) The object pushes back with an equal and opposite force
c) The force is cancelled
d) No reaction is experienced by the object
Answer:
b) The object pushes back with an equal and opposite force
Question 12. What is the momentum of an object of mass m, moving with a velocity v?
a) (mv)²
b) mv²
c) ½ mv²
d) mv
Answer:
d) mv
Question 13. A hockey ball of mass 200 g traveling at 10 m/s is struck by a hockey stick so as to return it along its original path with a velocity at 5 m/s. Calculate the magnitude of change of momentum occurred in the motion of the hockey ball by the force applied by the hockey stick.
a) 3 kg m/s
b) 2 kg m/s
c) 1.5 kg m/s
d) 1 kg m/s
Answer:
c) 1.5 kg m/s
Question 14. A bullet of mass 10 g traveling horizontally with a velocity of 150 m/s strikes a stationary wooden block and comes to rest in 0.03 s. Calculate the distance of penetration of the bullet into the block.
a) 0.5 m
b) 0.75 m
c) 2.25 m
d) 4.5 m
Answer:
c) 2.25 m
Question 15. An object of mass 1 kg traveling in a straight line with a velocity of 10 m/s collides with, and sticks to, a stationary wooden block of mass 5 kg. Calculate the velocity of the combined object.
a) 1.67 m/s
b) 2 m/s
c) 5 m/s
d) 10 m/s
Answer:
b) 2 m/s
Question 16. An object of mass 100 kg is accelerated uniformly from a velocity of 5 m/s to 8 m/s in 6 s. Calculate the magnitude of the force exerted on the object.
a) 50 N
b) 100 N
c) 150 N
d) 200 N
Answer:
a) 50 N
Question 17. How much momentum will a dumb-bell of mass 10 kg transfer to the floor if it falls from a height of 80 cm?
a) 8 kg m/s
b) 10 kg m/s
c) 12 kg m/s
d) 14 kg m/s
Answer:
a) 8 kg m/s
Question 18. When a carpet is beaten with a stick, dust comes out of it due to:
a) Inertia
b) Friction
c) Gravity
d) Air resistance
Answer:
a) Inertia
Question 19. A 8000 kg engine pulls a train of 5 wagons, each of 2000 kg, along a horizontal track. If the engine exerts a force of 40000 N and the track offers a friction force of 5000 N, the acceleration of the train is:
a) 2 m/s²
b) 3 m/s²
c) 4 m/s²
d) 5 m/s²
Answer:
b) 3 m/s²
Question 20. An automobile vehicle of mass 1500 kg needs a force to be stopped with a negative acceleration of 1.7 m/s². This force is:
a) 2550 N
b) 2050 N
c) 1750 N
d) 1500 N
Answer:
a) 2550 N
Question 21. The tendency of a body to resist any change in its state of rest or motion is known as __________.
Fill in the blank.
Answer:
Inertia
Question 22. An unbalanced force applied on an object changes its __________.
Fill in the blank.
Answer:
Velocity
Question 23. The SI unit of momentum is __________.
Fill in the blank.
Answer:
Kilogram meter per second (kg m/s)
Question 24. When an object undergoes uniform circular motion, its __________ changes.
Fill in the blank.
Answer:
Direction
Question 25. The rate of change of momentum of an object is proportional to the __________ applied on it.
Fill in the blank.
Answer:
Force
Question 26. Newton’s first law of motion is also known as the law of inertia. (True/False)
Answer:
True
Question 27. Momentum is a scalar quantity. (True/False)
Answer:
False
Question 28. The mass of an object is a measure of its inertia. (True/False)
Answer:
True
Question 29. Acceleration is produced when a force acts on a mass. The greater the mass, the greater the amount of force needed. (True/False)
Answer:
True
Question 30. Action and reaction forces act on the same object. (True/False)
Answer:
False
Question on Match the Columns
Unmatched Columns – Questions
| Column A | Column B |
|---|---|
| (i) Newton’s First Law of Motion | (a) Force is the product of mass and acceleration |
| (ii) Newton’s Second Law of Motion | (b) Action and reaction forces are equal and opposite |
| (iii) Newton’s Third Law of Motion | (c) Objects in motion stay in motion unless acted upon by an external force |
| (iv) Law of Conservation of Momentum | (d) Momentum is conserved in an isolated system |
| (v) Inertia | (e) Resistance of an object to a change in its state of motion |
| (vi) Momentum | (f) Mass times velocity of an object |
Matched Columns – Answer
| Column A | Column B |
|---|---|
| (i) Newton’s First Law of Motion | (c) Objects in motion stay in motion unless acted upon by an external force |
| (ii) Newton’s Second Law of Motion | (a) Force is the product of mass and acceleration |
| (iii) Newton’s Third Law of Motion | (b) Action and reaction forces are equal and opposite |
| (iv) Law of Conservation of Momentum | (d) Momentum is conserved in an isolated system |
| (v) Inertia | (e) Resistance of an object to a change in its state of motion |
| (vi) Momentum | (f) Mass times velocity of an object |
