1. Machines 5. Compound Machines

2. Try pulling a nail out of wood with your fingers
It is very hard to do

3. But with the end of a claw hammer
It is easy to get the nail out

4. The hammer is a 1st class lever
It increases the force you put on the nail

5. Compound machines can make work even easier than simple machines
Vocabulary:
Compound machine
A simple machine connect to one or more simple machines

6. In a compound machine the force you pass on to one simple machine
is made larger and passed on to another simple machine

7. The total force is made much larger
In this way
The total force is made much larger
Compound machines are all around you

8. A scissors is a compound machine
It is simply two levers,
With a fulcrum where the pin is

9. A can opener is a compound machine
The two handles are levers

10. The key you turn to open a can is a wheel and axle
The blade that cuts into the can is a wedge

11. A bicycle is another compound machine
Its wheels are connected to axles
so they make a wheel-and-axle machine

12. The brake handles are levers

13. A machine cannot make energy but every machine needs energy
When you pedal a bicycle
you provide the energy

14. Many machines use electric energy

15. All machines waste energy
Remember that friction is a force that resists motion

16. Machines usually have moving parts that rub against each other
Friction slows down the motion of the parts

17. The work done by a machine is always less than the work put into it
So energy is wasted
The work done by a machine is always less than the work put into it