# Pushing and Pulling

Push and pull are examples of forces experienced in the world every day. A force called friction happens when two items are rubbed against each other. Friction makes things go slower. Gravity is a force which pulls things down to the earth. Whenever a person drops something, gravity pushes it down to the ground or floor.

Pushing a baby stroller is an example of a force. It moves something farther along from where it was. If the stroller is pushed harder, it goes farther. Another example of pushing as a force is when a mother pushes a child on a swing. When she gives the swing a gentle push, the swing goes just a little. If she pushes it hard, the swing goes much higher. The harder an object, like a sled, is pulled, the farther it will go. A child's toy called a Slinky is a good example of both pushing and pulling as it goes down the stairs. It is pushed at the top, and then at each successive step, it is pulled down.

Every type of force is just really a push or pull. Some forces include contact and some do not. Magnetism either pulls an object toward it or pushes it away. It is a force. Pressure is a force where weight is applied to an object. If a door seems stuck, pushing it hard with a force called pressure may open it. If the door is pushed too hard, it may hit something or someone on the other side. Another example of pressure or weight as a force is leaving footprints on cement from dirty shoes. The person's weight applies pressure.

If the door opens toward a person, he may want to pull it. If he pulls it gently, it may open a little. If he pulls it very hard, it may knock him backward and bang against the wall. Springs and elastic bands are types of forces also. The harder a spring is stretched, the more it bounces back.

Sir Isaac Newton studied gravity and force. He proposed three laws. The first says that an object in motion, or moving, usually stays in motion. An object sitting still stays motionless. A car driving down the street will probably keep on moving. A ball rolling down the driveway will keep on rolling.

The second law says that an object's direction or speed will be changed if some kind of force acts against it. A ball may hit a wall and change direction. The third law says that there is an equal reaction to every action or force. If you kick a ball lightly, it will only go a short way. If you kick it hard, it will go farther.

Everything which has a mass or weight will most likely slow down at some point due to its weight. Inertia is the state of being still. Larger and heavier objects have more inertia and need more force to be moved.

Sometimes two forces work together on an object. Their joint efforts produce more force. For example, if two children start to push a sled down a hill, it will go farther and faster than if one did it alone. Two forces could also work against each other. If two girls want the same doll and are both trying to pull on it to get it for themselves, the forces will work against each other, and neither may get it unless one force is stronger.

Even three forces could act upon an object. A boy throws a ball. His throw is a force forward. Then gravity is a force which tries to pull it down. Also, the force of air resistance will slow the ball down.

We see powerful forces in weather too. Strong winds going one way can pull a tree's branches that way. Sometimes strong winds can push a car over. Heavy snow on a tree can push it over, along with gravity.

A: Gravity
B: Pushing
C: Pulling
D: Inertia

A: Sir Isaac Newton wrote a book about electricity.
B: More than one force can act upon an object.
C: Gravity pulls things down.
D: Magnets can either push or pull.

A: Magnetism
B: Pressure
C: Pulling
D: None of the above

A: Gravity
B: Magnetism
C: Pushing
D: Friction

A: Larger objects need more force to be moved.
B: Magnetism only pulls objects together.
C: Most forces are some kind of push or pull.
D: Both b and c

A: Third
B: Fourth
C: First
D: Second

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