Class 9 Science Chapter 6 MCQs – How Forces Affect Motion

Class 9 Science Chapter 6 MCQs – How Forces Affect Motion provides 50 important multiple-choice questions with answers to help students revise force, balanced and unbalanced forces, inertia, Newton’s laws of motion, momentum, acceleration, and friction. These MCQs are useful for Class 9 Science exam preparation and concept revision.

1. What is a force?

A. A type of energy
B. A push or pull acting on an object
C. The speed of an object
D. The mass of an object

Answer: B. A push or pull acting on an object

2. The SI unit of force is:

A. Joule
B. Watt
C. Newton
D. Pascal

Answer: C. Newton

3. A force can change the:

A. State of motion of an object
B. Shape of an object
C. Direction of motion
D. All of the above

Answer: D. All of the above

4. Which of the following is a contact force?

A. Gravitational force
B. Magnetic force
C. Frictional force
D. Electrostatic force

Answer: C. Frictional force

5. Which of the following is a non-contact force?

A. Friction
B. Muscular force
C. Gravitational force
D. Normal force

Answer: C. Gravitational force

6. When two or more forces acting on an object have a resultant force of zero, they are called:

A. Unbalanced forces
B. Balanced forces
C. Magnetic forces
D. Frictional forces

Answer: B. Balanced forces

7. Balanced forces can:

A. Always change the speed of an object
B. Always change the direction of motion
C. Change the shape of an object
D. Always produce acceleration

Answer: C. Change the shape of an object

8. An unbalanced force acting on an object can change its:

A. State of motion
B. Colour
C. Temperature only
D. Chemical composition only

Answer: A. State of motion

9. Newton’s First Law of Motion is also known as the law of:

A. Momentum
B. Inertia
C. Gravitation
D. Acceleration

Answer: B. Inertia

10. The tendency of an object to resist a change in its state of motion is called:

A. Momentum
B. Inertia
C. Force
D. Acceleration

Answer: B. Inertia

11. Which physical quantity is a measure of inertia?

A. Speed
B. Mass
C. Velocity
D. Acceleration

Answer: B. Mass

12. Which object has the greatest inertia?

A. A 1 kg ball
B. A 2 kg ball
C. A 5 kg ball
D. A 10 kg ball

Answer: D. A 10 kg ball

13. A passenger in a moving bus tends to move forward when the bus suddenly stops because of:

A. Friction
B. Inertia of motion
C. Inertia of rest
D. Gravity

Answer: B. Inertia of motion

14. When a stationary bus suddenly starts moving, passengers tend to fall backward because of:

A. Inertia of rest
B. Inertia of motion
C. Friction
D. Gravity

Answer: A. Inertia of rest

15. Dust is removed from a carpet by beating it because of:

A. Inertia of rest
B. Inertia of motion
C. Gravitational force only
D. Magnetic force

Answer: A. Inertia of rest

16. Newton’s Second Law of Motion relates force with:

A. Mass and acceleration
B. Mass and volume
C. Speed and distance
D. Density and volume

Answer: A. Mass and acceleration

17. The mathematical expression for Newton’s Second Law is:

A. F = m/a
B. F = ma
C. F = a/m
D. F = m + a

Answer: B. F = ma

18. If the mass of an object is doubled while the applied force remains constant, its acceleration becomes:

A. Double
B. Half
C. Four times
D. Unchanged

Answer: B. Half

19. If the force acting on an object is doubled while its mass remains constant, its acceleration becomes:

A. Half
B. Double
C. Four times
D. Zero

Answer: B. Double

20. A force of 10 N acts on a mass of 2 kg. What is its acceleration?

A. 2 m/s²
B. 5 m/s²
C. 10 m/s²
D. 20 m/s²

Answer: B. 5 m/s²

21. A force of 20 N acts on a body of mass 5 kg. Its acceleration is:

A. 2 m/s²
B. 4 m/s²
C. 5 m/s²
D. 10 m/s²

Answer: B. 4 m/s²

22. Momentum is defined as the product of:

A. Mass and acceleration
B. Force and time
C. Mass and velocity
D. Force and distance

Answer: C. Mass and velocity

23. The SI unit of momentum is:

A. kg m/s
B. kg/m/s
C. N/m
D. kg m/s²

Answer: A. kg m/s

24. Which object has greater momentum if both objects have the same velocity?

A. The object with smaller mass
B. The object with greater mass
C. Both always have equal momentum
D. Momentum does not depend on mass

Answer: B. The object with greater mass

25. If the velocity of an object becomes zero, its momentum becomes:

A. Maximum
B. Minimum but not zero
C. Zero
D. Infinite

Answer: C. Zero

26. Newton’s Third Law of Motion states that:

A. Force equals mass × acceleration
B. Every action has an equal and opposite reaction
C. Objects always remain at rest
D. Momentum is always zero

Answer: B. Every action has an equal and opposite reaction

27. When a person pushes a wall, the wall:

A. Exerts no force
B. Exerts an equal and opposite force on the person
C. Moves away immediately
D. Loses its mass

Answer: B. Exerts an equal and opposite force on the person

28. A rocket moves upward because:

A. It pushes gases downward and gases exert an upward force on the rocket
B. Gravity pushes it upward
C. Air pushes it upward only
D. Its mass becomes zero

Answer: A. It pushes gases downward and gases exert an upward force on the rocket

29. When a swimmer pushes water backward, the swimmer moves:

A. Backward
B. Forward
C. Sideways only
D. Downward

Answer: B. Forward

30. The forces in an action-reaction pair:

A. Act on the same object
B. Act on different objects
C. Always act in the same direction
D. Have different magnitudes

Answer: B. Act on different objects

31. Which of the following is an example of muscular force?

A. A magnet attracting iron
B. A person lifting a bag
C. Earth attracting an object
D. A charged comb attracting paper

Answer: B. A person lifting a bag

32. The force that opposes relative motion between two surfaces in contact is:

A. Gravitational force
B. Magnetic force
C. Frictional force
D. Electrostatic force

Answer: C. Frictional force

33. Friction generally acts:

A. In the direction of motion
B. Opposite to relative motion or its tendency
C. Vertically upward only
D. Vertically downward only

Answer: B. Opposite to relative motion or its tendency

34. Which type of friction acts when an object rolls over a surface?

A. Static friction
B. Sliding friction
C. Rolling friction
D. Fluid friction only

Answer: C. Rolling friction

35. Which is generally smaller for the same surfaces?

A. Static friction
B. Sliding friction
C. Rolling friction
D. All are always equal

Answer: C. Rolling friction

36. Why are wheels used in vehicles?

A. To increase sliding friction
B. To reduce friction by converting sliding into rolling
C. To increase mass
D. To stop motion

Answer: B. To reduce friction by converting sliding into rolling

37. Lubricants are used in machines mainly to:

A. Increase friction
B. Reduce friction
C. Increase mass
D. Increase gravity

Answer: B. Reduce friction

38. Friction is useful when:

A. We walk on the ground
B. We want to reduce wear in machines
C. We want to reduce heat production
D. We want objects to slide easily

Answer: A. We walk on the ground

39. The soles of shoes have grooves mainly to:

A. Reduce grip
B. Increase friction with the ground
C. Reduce mass
D. Increase speed automatically

Answer: B. Increase friction with the ground

40. Tyres of vehicles have treads mainly to:

A. Reduce contact with the road
B. Increase friction and improve grip
C. Increase the mass of the vehicle
D. Eliminate friction completely

Answer: B. Increase friction and improve grip

41. If the net force acting on an object is zero, the object:

A. Must always be at rest
B. Must always accelerate
C. May remain at rest or move with constant velocity
D. Must move in a circle

Answer: C. May remain at rest or move with constant velocity

42. Two forces of 10 N each act on an object in opposite directions. The resultant force is:

A. 20 N
B. 10 N
C. 5 N
D. 0 N

Answer: D. 0 N

43. Two forces of 15 N and 5 N act in the same direction. Their resultant force is:

A. 10 N
B. 15 N
C. 20 N
D. 75 N

Answer: C. 20 N

44. Two opposite forces of 25 N and 10 N act on an object. The magnitude of the resultant force is:

A. 35 N
B. 25 N
C. 15 N
D. 10 N

Answer: C. 15 N

45. If no external unbalanced force acts on a moving object, it will:

A. Immediately stop
B. Continue moving with constant velocity
C. Always accelerate
D. Change direction automatically

Answer: B. Continue moving with constant velocity

46. A seat belt protects passengers mainly because it:

A. Increases their mass
B. Prevents their body from continuing forward due to inertia when the vehicle stops suddenly
C. Eliminates gravity
D. Increases the speed of the vehicle

Answer: B. Prevents their body from continuing forward due to inertia when the vehicle stops suddenly

47. Why does a person lean backward when a bus starts suddenly?

A. Due to inertia of rest
B. Due to inertia of motion
C. Due to magnetic force
D. Due to friction alone

Answer: A. Due to inertia of rest

48. A cricketer moves his hands backward while catching a fast ball. This helps to:

A. Increase the change in momentum per unit time
B. Increase the force on his hands
C. Increase the time over which momentum changes, reducing the force
D. Stop the ball without applying any force

Answer: C. Increase the time over which momentum changes, reducing the force

49. A force of 50 N acts on an object of mass 10 kg. The acceleration produced is:

A. 2 m/s²
B. 5 m/s²
C. 10 m/s²
D. 500 m/s²