Work, Force and Energy Notes

INTRODUCTION

•      Living things can move by themselves.

•      Non-living things cannot move by themselves.

•      There should be a force to make them move.

•      To drive a bicycle, we apply force with our feet to produce motion.

•      Thus we can say that force is required in producing motion in the body. For example the box does not move although the push of the person tends to move it.

FORCE

•      A push or pull acting on an object is called force.

•      Force make things move or make things change their motion.

(a)                                (b)

Figure 1: (a) A weightlifter is lifting (pulling) the weight

(b) A soldier is firing bullet from a machine gun

•      Two natural forces that affect most of the motion we are aware of are the force of gravity and electromagnetic forces.

•      Gravity is one of the universal forces of nature. It is the force of attraction by which terrestrial bodies tend to fall towards the center of the earth.

EFFECTS OF FORCE

•      We cannot see force, but we can see its effects. The effects that a force can have on objects are:

1. A force can change the direction in which an object is moving.

For example:

•      Motion is a change of position.

•      When a person throws a ball, he or she puts it in motion and the position of the ball changes.

•      When a baseball player runs around the bases, his or her position changes.

•      Even, the force applied by the baseball batsman, changes the direction of the ball that is bowled at him/her.