66 Force and Motion-Mid

Force and Motion Written by Ron Fridell

Introduction Each word above tells how objects can move. Some travel in a straight, flat line such as a ball rolled along the ground. When you kick the ball into the air, it flies in a curved path until it bounces on the ground. A merry-go-round turns in circles, while lightning strikes in a jagged path. Motion is all around you. It's even inside you as your blood moves through your body. For every motion, there is a force. In this book, you will learn about the forces that make things move, stop, and change direction or speed.

Motion Needs a Force To make something move, a force is needed. Lifting, pushing, and pulling are all forces. At times, a person provides the force. When you lift a stack of books, push a broken-down car, or pull a rope in a tug-of-war game, you are the force.

Machines can provide force to create motion. A huge engine can produce enough force to propel a massive rocket into space. Motors in cake mixers, fans, and blenders use electrical force to make things move. Nature can also be a strong force. Breezes make leaves dance in the treetops. Ocean waves make boats bob up and down. Forces deep underground cause earthquakes that make the ground tremble.

The Laws of Motion Much of what we know about motion comes from scientists who lived hundreds of years ago. They conducted tests on moving objects. British scientist Isaac Newton discovered gravity the invisible force that causes things to fall toward the ground. You may have heard that he was sitting under a tree one day when a falling apple hit him on the head. The story goes that this accident led him to discover gravity. Isaac wasn't really hit on the head by a falling apple. That's just a myth. But over time, he observed that objects always fall down toward the ground. And that led him to discover gravity. SIR LSAAC NEWTON (1642-1727) Isaac Newton lived on a farm in England. Instead of farming, he chose to study math and science in London. At age 27, Isaac did experiments with light He was the first to suggest that light. was actually 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, which explain how things move. The first part of the first law says that an object at rest will remain at rest unless a force acts upon it. For example, your bike will stay parked where it is unless something moves it. The second part of this law states that an object in motion will continue moving in the same way unless a new force changes the motion. It will keep moving at the same speed and in the same direction. So your moving bike will continue moving at the same speed and in the same direction until you pedal faster, coast, brake, or turn. Word Wise In government, a law is a rule that people must obey. In science a law is a statement that explains how things always work in the physical world.