CHAPTER 1 WHAT IS ENERGY A farmer wants to plant seeds But first she needs to make the ground ready So she turns the key on her tractor The engine roars to a start The farmer drives the tractor to prepare the ground Vehicles such as tractors need energy to move 5
How is the farmer able to drive the tractor It is a result of energy Energy cannot be created or destroyed But it can change forms Many things can cause an object’s energy to change One way is if work is done on the object Work may be done when a force acts on a moving object Work can be positive or negative It depends in part on the direction that the object is moving Work is positive if the force points 6
Plants use energy from the sun in the same direction Work is negative if the force points in the opposite direction 7
