Class 9 Physics MCQs: Dynamics - II

MCQs (sample)

Showing 25 questions from this chapter. For a full timed test, use “Start online test”.

1. 1. What is an orbit?

   • A regular path an object takes around another object in space.
   • A random path taken by an object in space.
   • A straight line path of a satellite.
   • A point in space where no objects move.
   Answer & explanation

   Correct: A regular path an object takes around another object in space.

   An orbit is defined as a regular, repeating path that one object in space takes around another.

2. 2. What is uniform circular motion?

   • Motion with constant speed in a straight line
   • Motion with constant speed in a circular path
   • Motion with changing speed along a circular path
   • Motion with changing direction but no speed change
   Answer & explanation

   Correct: Motion with constant speed in a circular path

   Uniform circular motion refers to motion with constant speed in a circular path.

3. 3. What is the turning effect produced by a force on a body called?

   • Moment of force
   • Mass
   • Velocity
   • Acceleration
   Answer & explanation

   Correct: Moment of force

   The turning effect produced in a body due to applied force is called moment of force (or torque).

4. 4. What is the definition of stability?

   • A measure of the ability of an object to return to its original position when a force is removed.
   • A measure of an object's weight.
   • A measure of how quickly an object moves.
   • A measure of the size of an object.
   Answer & explanation

   Correct: A measure of the ability of an object to return to its original position when a force is removed.

   Stability is defined as the ability of an object to return to its original position when the force that changed its position is removed.

5. 5. What is the line along which a force acts called?

   • Line of action
   • Net force
   • Direction of force
   • Force vector
   Answer & explanation

   Correct: Line of action

   The line along which a force acts is called the line of action of the force.

6. 6. What is the center of mass (CM) of a rigid body?

   • The point about which mass is equally distributed.
   • The point where the weight of the body is focused.
   • The point where deformation occurs in the body.
   • The point that determines the shape of the body.
   Answer & explanation

   Correct: The point about which mass is equally distributed.

   The center of mass (CM) is defined as the point about which mass is equally distributed in a rigid body.

7. 7. What is the unit of friction?

   • Newton (N)
   • Pascal (Pa)
   • Joule (J)
   • Watt (W)
   Answer & explanation

   Correct: Newton (N)

   Friction is a force and its unit is newton (N).

8. 8. What is equilibrium in physics?

   • All forces and moments are balanced.
   • Only forces are balanced.
   • Only torques are balanced.
   • Forces and torques do not matter.
   Answer & explanation

   Correct: All forces and moments are balanced.

   Equilibrium is defined as a state where all individual forces and moments are balanced, resulting in a net force and torque of zero.

9. 9. Which of the following is considered a natural satellite?

   • The Moon
   • The International Space Station
   • A weather balloon
   • A communication satellite
   Answer & explanation

   Correct: The Moon

   The Moon is a natural satellite as it orbits the Earth.

10. 10. In uniform circular motion, what remains constant?

    • The speed of the object
    • The direction of the velocity
    • The radius of the circle
    • The velocity of the object
    Answer & explanation

    Correct: The speed of the object

    In uniform circular motion, the speed of the object remains constant while its direction changes.

11. 11. Which of the following quantities is moment of force?

    • Vector quantity
    • Scalar quantity
    • Constant quantity
    • None of the above
    Answer & explanation

    Correct: Vector quantity

    Moment of force (or torque) is a vector quantity.

12. 12. What happens to the center of mass when a body in stable equilibrium is displaced?

    • It rises.
    • It falls.
    • It stays the same.
    • It moves sideways.
    Answer & explanation

    Correct: It rises.

    In a stable equilibrium, the center of mass rises when the body is displaced.

13. 13. What do you call multiple forces acting on bodies at the same time?

    • Net force
    • Parallel forces
    • Individual forces
    • Resultant forces
    Answer & explanation

    Correct: Parallel forces

    Multiple forces acting on bodies at the same time are called parallel forces.

14. 14. What happens when the line of action of force passes through the center of mass of a body?

    • It will produce rotation.
    • It will not produce any rotation.
    • It will increase the velocity.
    • It will decrease the object's weight.
    Answer & explanation

    Correct: It will not produce any rotation.

    If the line of action of force passes through the center of mass, it will not produce any rotation in the body.

15. 15. What direction does friction act in relation to motion?

    • In the direction of motion
    • Opposite to the direction of motion
    • Perpendicular to the motion
    • No specific direction
    Answer & explanation

    Correct: Opposite to the direction of motion

    Friction always acts in a direction to oppose motion.

16. 16. What satisfies the first condition of equilibrium?

    • The vector sum of all forces is zero.
    • The vector sum of all torques is zero.
    • All forces are equal in magnitude.
    • The object is in motion.
    Answer & explanation

    Correct: The vector sum of all forces is zero.

    The first condition of equilibrium is satisfied when the vector sum of all forces acting on an object is zero.

17. 17. What is an artificial satellite?

    • A satellite that occurs naturally in space.
    • A man-made object that orbits Earth or another body.
    • A star that emits its own light.
    • A planet's moon.
    Answer & explanation

    Correct: A man-made object that orbits Earth or another body.

    An artificial satellite is a man-made object that is sent into orbit around Earth or another body.

18. 18. What changes in uniform circular motion despite constant speed?

    • Mass
    • Velocity
    • Radius
    • Centripetal force
    Answer & explanation

    Correct: Velocity

    Although speed remains constant, the direction of the object continuously changes, leading to a change in velocity.

19. 19. What is the SI unit of moment of force?

    • N m
    • kg m/s²
    • Joule
    • Watt
    Answer & explanation

    Correct: N m

    The SI unit of moment of force is N m (Newton meter).

20. 20. How does an unstable equilibrium behave when a body is slightly displaced?

    • It returns to its original position.
    • It moves further away from its previous position.
    • It stays in its new position.
    • It spins around.
    Answer & explanation

    Correct: It moves further away from its previous position.

    A body in unstable equilibrium moves further away from its original position when slightly displaced.

21. 21. When forces act in the same direction, they are referred to as what?

    • Unlike parallel forces
    • Net forces
    • Like parallel forces
    • Unit forces
    Answer & explanation

    Correct: Like parallel forces

    Forces acting in the same direction are called like parallel forces.

22. 22. For small objects, how does the center of mass compare to the center of gravity?

    • They are always different.
    • They are the same.
    • Center of mass is higher than center of gravity.
    • Center of gravity is always at the top of the object.
    Answer & explanation

    Correct: They are the same.

    The center of mass (CM) and center of gravity (CG) are the same for small objects.

23. 23. What type of friction slows down a bike when brake pads contact the rims?

    • Static friction
    • Sliding friction
    • Rolling friction
    • Fluid friction
    Answer & explanation

    Correct: Sliding friction

    Sliding friction is the resistance created when two objects slide against each other, such as brake pads on rims.

24. 24. What satisfies the second condition of equilibrium?

    • The vector sum of all forces is zero.
    • The vector sum of all torques is zero.
    • The object is at rest.
    • The object has no mass.
    Answer & explanation

    Correct: The vector sum of all torques is zero.

    The second condition of equilibrium is satisfied when the vector sum of all torques acting on an object is zero.

25. 25. What does gravity do in relation to satellites?

    • Prevents them from orbiting.
    • Causes them to float away.
    • Keeps them in orbit around another body.
    • Makes satellites crash.
    Answer & explanation

    Correct: Keeps them in orbit around another body.

    Gravity is the force that keeps satellites in orbit around other bodies.