Force

                  Force

 When we want to open a door, we have to push the door handle. And when we want to close the door, we have to pull the door handle with our hands. This means that to move a body or an object, it has either to be pushed or pulled. 

         A push or pull on a body is called force. The direction in which a body is pushed or pulled is called the direction of force.

        Forces are used in our everyday actions like pushing, pulling, lifting, stretching, twisting and pressing.

For example - A force is used when we push (kick) a football.

 Effects of force - 

 

  A force cannot be seen. A force can be judged only by the effects which it can produce in various bodies or objects around us . A force can produce the following effects - 

1) A force can move a stationary body.

2) A force can stop a moving body.

3) A force can change the speed of a moving body.

4) A force can change the direction of a moving body.

5) A force can change the shape and size of a body.

Balanced and unbalanced forces

 Forces are of two types- 

1) Balanced forces

2) Unbalanced forces

(1) Balanced forces -

 If the resultant of all the forces acting on a body is zero , the forces are called balanced forces.

Balanced forces cannot produce motion in a stationary body or stop a moving body, they can however, change the shape of the body.

For example- 

Suppose a heavy box is lying on the ground. Let us push this box with our hands. We find that the box does not move, though as many as forces are acting on it.

(2) Unbalanced forces - 

 

  If the resultant of all the forces acting on a body is not zero , the forces are called unbalanced forces.

Unbalanced forces can move a stationary body or they can stop a moving body.

For example- 

Suppose a toy car is lying on the ground. Let us push this car with our hands. We find that the toy car starts moving.