65 Force and Motion-Low

Force and Motion Written by Ron Fridell

Introduction The words above tell about motion. They describe different ways things move. Motion is all around you. There is even motion inside you Your blood is moving right now. For every motion, there is a force. In this book, you will learn about motion and the forces that make things move.

Motion Needs a Force You need a force to move something. Lifting, pushing, and pulling are all forces. Where do forces come from? Sometimes the force comes from a person. When you lift your books, you are the force. If you push a car, you are the force. If you pull a rope to play tug-of-war, you are the force.

Machines can be a force. A huge engine can push a rocket into space. A small electric motor can turn the blades of a fan or power a toy car. Nature is also a force. Breezes make leaves shake in the treetops. Ocean waves make boats bob in the water. Earthquakes shake the ground.

The Laws of Motion Scientists have done tests on motion for hundreds of years. British scientist Isaac Newton discovered the force we call gravity. You cannot see gravity. But it causes things to fall toward the ground. Some people think that Newton discovered gravity when a falling apple hit him on the head. That's not true. But Newton did notice that things always fell down toward the ground. He would watch closely and make notes. That is how he discovered gravity. SIR LSSAC NEWTON (1642-1727) Isaac Newton lived on a farm in England. Instead of farming, he chose to study math and science. He made many important discoveries. At age 27, Newton did tests on light. He was the first person to state that light was made up of all the colors of the rainbow. He is now one of the most famous scientists of all time!

Newton's First Law of Motion Isaac Newton is known for his three laws of motion. These laws explain how things move. The first law has two parts. Part one says that an object at rest will not move unless a force moves it. For example, your bike will stay parked until something moves it. Part two says that an object will keep moving in the same way unless a new force changes how it moves. It will keep moving at the same speed and in the same direction. If you pedal your bike faster or turn, your bike will change speed or direction. If you brake it will stop. Word Wise A law is a rule that people must follow. But in science, law has another meaning. A law explains how things in the world always work.