Push or pull

Many objects will move if you push or pull them.

 A push and a pull is a force.An object will move when you lift it .Lighting is a force.

HOW MUCH FORCE?

Pretend that you are going to clean the room.You have to lift many objects off the floor to put them away.Sometimes you use a large force to lift object.Sometimes you use only a small force.

The amount of force needed to move an object depends on how much of that one object there is.While you are cleaning,you find two boxes.Both boxes are the same size.One is filled with rocks.One is filled with stamps.

ANOTHER PULLING FORCE

What happens to a kite when you pull on its strings?Just as you pull on objects,too!It even pulls on you.You can feel the pull when you jump up in the air.The pull between the Earth.When you throw a ball,gravity pulls it back to Earth.

WORK AND ENERGY

You have learned that forces cause objects to move.Scientists say that work is done when a force moves an object.

To fine the amount of work  done,you must know how much force is needed to move an object.Some objects need more force than others to moved.You must also know how far the object is moved.The amount of work done depends on both force and distance.More work is done if a wagon is pulled ten meters instead of five meters.

A nail is forced into a board when hit by a hammer.Objects may move when they are pushed or pulled by a force.Each time a force moves an object,such as a books and a nail,work is done.When  work is done energy is used.Energy is the ability to do work.The girls can do work because they have energy.You are able to do work because they have energy too.The work you do, the more energy you use.

SIMPLE MACHINES

Work can be made easier by using machines.People use machines to move objects.They use many kinds of machines.Machines with few or no moving parts are called simple machines.Each pf these objects is a simple machine.

LEVER

All levers use three parts.Any object to be lifted is called the load.The point where the lever rocks back and forth is called fulcrum.A push or a pull that moves the level is called a force.

ICLINED PLANE

An inclined plane is a simple machine used to moves objects to a higher place.A ramp is an inclined plane.A sidewalk going up a hill is  an  inclined plane,too.A wedge(WEJ) is a simple machine made of two inclined planes.Force moves the wedge when the work is done.Sometimes a wedge is used to push objects apart.

You can know the force needed to raise an object with an inclined plane depends on the distance moved.A longer distance is covered when the inclinded plane is wrapped around a post.A screw is an inclined plane that is wrapped around a post.Since a longer distance is covered,less force is used to turn a srew than to pound a nali into a piece of wood.

WHEEL AND AXLE

A wheel and axle is a simple machine with a wheel that turns on a post.The post is called an axle.

Pulley

A pulley is a simple machine used to lift heavy loads.It can also move objects to places that are hard to reach.

What type of force is used with these pulleys?Sometimes it is easier to pull on objects than to push on them.Sometimes less force is needed to lift the objects when a pulley is used.

Pulleys can also be used to change the direction of a force.Changing the direction of a force may make work easier to do.