# A Force can Change the Speed of a Moving Object

Suppose we are moving on a bicycle at a certain speed. Now, if someone pushes the moving bicycle from behind, then the speed of bicycle increase and it will move faster. On the other hand, if someone pulls the moving bicycle from behind, then the speed of bicycle decreases and it will move slower. Thus, a push or pull can change the speed of a moving bicycle. But a push a push or pull is called force. So, we can say that a force can change the speed of a moving bicycle (or any other moving object). If the force is applied in the direction of motion of the object, its speed increase. On the other hand, if the force is applied in the direction opposite to the direction of motion of an object, then its speed decreases.

When a ball is dropped form a height, its speed goes on increasing. The speed of a falling object (like a ball) increases because the earth applies a pulling force on it which is called the force of gravity. It is the force of gravity of the earth which is called the force of gravity. It is the applies a pulling force on it which is called the force of gravity. It is the force of gravity of the earth which pulls a falling object towards its center and increases its speed. On the other hand, when a ball is thrown upwards, then its speed goes on decreasing. This is because the earth exerts a pulling force of gravity in the downward direction (as opposed to the movement of the ball). When the hockey player hits the moving ball, the speed of the ball increases. When we pedal the bicycle faster, then the speed of bicycle decreases. Form all these examples we conclude that a force can change the speed of a moving object.

## A Force can Change the Direction of a Moving Object

In a cricket match, when a moving cricket ball is hit by a bat, then the direction of cricket ball changes and it goes in another direction. In this case, the force exerted by bat changes the direction of a moving cricket ball. In the game of carom, when we take a rebound, then the direction of striker changes. This is because the edge of the carom board exerts a force on the striker. If we blow air from our mouth on the smoke changes. In this case, the force exerted by the blowing air changes the direction of moving smoke. From these examples we conclude that a force can change the direction of motion of a moving object.

# A Force can Change the Shape and Size of an Object

If we take a light spring and pull it at both the ends with our hands, then the shape and size of the spring changes. In this case, the force of our hands changes the shape and size of the spring (The turns of the spring become farther apart and its length increases). Here are some more examples in which a force changes the shape (or size) of an object. The shape of dough (kneaded wet flour) changes on pressing with a rolling pin (belan) to make chapatis.