Force and Motion MCQs Quiz | Class 9
Test your understanding of Class IX Science (Code 086), Unit III: Motion, Force and Work. This quiz covers the effect of force on motion, change in state, and practical examples like inertia and balanced forces. Attempt these 10 multiple-choice questions, check your score, and download the solution PDF for revision.
Unit III: Motion, Force and Work – Overview
Force is an external effort in the form of a push or a pull that changes or tends to change the state of rest or of motion of an object, or its direction or dimensions. In Class 9 Science, understanding the nature of force and its effects is crucial for mastering mechanics.
1. Effects of Force
A force acting on an object can cause several effects:
- Change in Speed: It can make a stationary object move or change the speed of a moving object.
- Change in Direction: It can change the direction of motion of a moving object.
- Change in Shape: It can change the shape or size of an object (e.g., squeezing a rubber ball).
2. Balanced and Unbalanced Forces
| Balanced Forces | Unbalanced Forces |
|---|---|
| Resultant force is zero. | Resultant force is not zero. |
| Do not change the state of rest or motion. | Change the state of rest or motion. |
| Example: Pushing a heavy wall that does not move. | Example: Pushing a toy car to make it move. |
3. Newton’s First Law of Motion
Also known as the Law of Inertia, it states that an object remains in a state of rest or of uniform motion in a straight line unless compelled to change that state by an applied force.
4. Inertia and Mass
Inertia is the natural tendency of an object to resist a change in its state of motion or of rest. The mass of an object is a measure of its inertia. Heavier objects have more inertia than lighter objects.
- Inertia of Rest: A passenger falls backward when a bus starts suddenly.
- Inertia of Motion: A passenger falls forward when a moving bus stops suddenly.
- Inertia of Direction: A passenger leans sideways when a bus takes a sharp turn.
Extra Practice Questions
- What is the CGS unit of force? (Answer: Dyne)
- Why does a luggage on the roof of a bus need to be tied with a rope? (Answer: To prevent it from falling due to inertia)
- If no external force acts on a moving body, how long will it continue to move? (Answer: Forever, due to inertia)
- What force opposes the motion of a ball rolling on the ground? (Answer: Friction)
- Can balanced forces change the shape of an object? (Answer: Yes, e.g., squeezing a balloon)
