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# Force – Effects and Types

## Effects of Force

### Key Concepts

• Effects of force
• Change of shape

### Introduction

A force comes into play when two or more objects interact with each other. This force when applied to an object by another, gives rise to some kind of change in the state of motion of an object. In this section we will be looking at these changes that a body undergoes when a force is applied on it.

### Effects of Force:

The changes that an object might undergo when a force is applied on it are called the effects of force. The following are the various effects that are caused when a force is applied by an object on another resulting in a change in its state of motion.

1. A force can start or stop the motion of a body:

When a boy stands near a football, the football does not move at all. It starts moving only when the body kicks it. Here, the football moves only when the boy applies a force on it. Thus, a force can make a stationary body move.

A football stops moving when a goalkeeper catches it and a cricket ball stops moving when a fielder catches it. Thus, a force can stop the motion of a moving body when it is applied in the direction opposite to that of the body’s motion.

1. A force can speed up or slow down the motion of a body.

When a football is kicked by a child, its speed increases to some extent. However, when they kick it harder, the football speeds up even more. Thus, a larger amount of force, when applied to an object, speeds up its motion. Therefore, a force can speed up the motion of an object when applied in the direction of motion of an object.

When brakes are applied in a car, its speed reduces. The application of brakes exert a force in a direction opposite to the direction of motion of the car. The car gradually slows down and eventually stops moving. Thus, a force can slow down the motion of an object when applied in a direction opposite to the direction of motion of an object.

1. A force can change the direction of motion of a body.

When hit by a bat a baseball changes its direction. When hit by an edge of a carom board, the striker changes its direction. These examples indicate that a force changes the direction of motion of a moving body.

Thus, a force, when applied to an object can make it move, stop its motion, speed up, slow down and/or change its direction of motion. In other words, a force, when applied to an object may change its state of motion.

However, it does not mean that the application of force would always lead to a change in the state of motion of an object. For example:

The wall does not move when it is pushed hard. A heavily loaded trolley does not move when it is pulled hard. A heavy dresser does not move when it is pushed.

At times, the applied force does not change the state of motion of the body, as the amount of force is insufficient to do so. Thus, no effect of force is observed in such cases.

## Change of shape:

Following are some of the common observations:

The shape of the pizza dough changes on kneading it.

The shape of the rubber band changes when it is stretched at the ends.

The shape of the lemon changes when pressed from two sides.

Thus, it can be concluded from the above observations that a force applied on an object may change its shape.

A force may cause one or more of the effects discussed above to a body, when applied on it. None of these actions (included under the effects of force) can take place without an application of force. Thus, an object cannot move or stop or change its speed or direction by itself. Whenever such actions take place, there will be a force causing it.

## Summary

1. The changes that an object might undergo when a force is applied on it are called the
effects of force.
2. A force may start or stop the motion of a body.
3. A force may speed up or slow down a moving body.
4. A force may change the direction of motion of a moving body.
5. A force may also change the shape of a body.
6. At times, the applied force does not change the state of motion of the body, as the
amount of force is insufficient to do so. Thus, no effect of force is observed in such cases.
7. An object cannot move or stop or change its speed or direction by itself. Whenever
such actions take place, there will be a force causing it.

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