Simple Machines

Forces and Motion

A force is a push or pull.

• You push on a door
• The force of the wind pushes sailboats and windmills

The amount of force you have to use to move an object depends on its mass.

• I bring a cardboard box (originally for apples) and a rope into the classroom. I chose a tall learner and a short learner. First the short learner sits down in the box and someone pushes him or her through the room. Then I tell the tall one to sit in the box. The learners laugh. They know, that it is much harder to push that one!

Motion is a change in position. Every motion is started and ended by a force.

• If we throw (pushing force) a ball and nobody is there to catch it, in theory, it could fly on forever, but gravity pulls it down and makes it stop on the ground.

Gravity is the force that causes all things to fall to the ground.

Simple Machines

A simple machine is a tool that helps people to do work.

There are six types of simple machines:

Lever

Pulley

Wheel and axle

Inclined plane

Wedge

Screw

I show the learners a lot of pictures and let them identify the type of simple machine.

Inclined plane

An inclined plane is a flat surface set at an ancle to another surface/the ground.

Example: A load is pushed along the inclined plane onto a truck.

We build an inclined plane using our rulers as an inclined plane and our rubbers/sharpeners as heavy load.

Screw

A screw is like an inclined plane wrapped around a pencil.

Example: Screw, bottletop

Lever

A lever is a bar that moves on or around a fixed point (called the fulcrum).

I demonstrate the fixed point to my learners with a red drawing-pin.

Examples:

• Arm
• Seesaw
• Balance scale
• Pair of tongs, pliers
• Pair of scissors
• Bottleopener
• Crowbar
• Wheelbarrow
• Hammer

We build a seesaw ourselves using a ruler, a pencil and a small object as a load. The pencil is the fixed point/fulcrum of the seesaw. The ruler is the bar. As small object you can use a rubber.

Wedge

A wedge is two inclined planes stuck back to back.

Example: An ax. A pair of scissors is made up of two wedges.

Wheel and axle

In a wheel and axle, the wheel is larger than the axle. It takes less force to move the wheel than to move the axle. But when the wheel makes a circle it goes a longer distance than the axle.

Example: Bycicle.

Pulley

A pulley is a rope over a wheel.

It changes the direction of the force that you use. When you pull down one end of the rope, the bucket at the other end moves up. Because of gravity, pulling down is much easier than pulling up. Pulling down there are two forces: you and gravity. Pulling up you have to fight gravity.

We build a pulley.

Materials needed: empty toilet tissue rolls, wool, a small object as `load´, a pencil.

Put the pencil through the paper roll. The pencil is the axle and the paper roll the wheel. Wind the wool two times around the roll and attach a load like a pencil sharpener to one end of the wool. Then pull down the other side of the wool and see how the load is moved up!

Simple Machines poem

It´s easy to find – a plane that is inclined!

The edge looks like a – wedge!

Ouch, in my shoe there is a – screw! Screw you!

I hurry to pull the – pulley!

I think it´s clever to use a – lever!

For an easy deal I use – axle and wheel!