1. How can a machine make work easier?
Work and Machines
What Do You Think?
How can a machine make work easier?

2. Work and Machines
Work occurs when a force causes an object to move in the direction of the force.
A machine is defined as something that makes work easier.

3. You know when work is done on an object if two things happen:
the object moves as a force is applied
the direction of the object’s motion is the same as the direction of the force applied.

4. Calculating Work
Work = Force x Distance (W= F x d)
The unit used to express work is the joule (J).

5. 1. Suppose you lift a 75 n bowling ball 2 m off the floor
1. Suppose you lift a 75 n bowling ball 2 m off the floor. How much work do you do?
2. How much work is required to lift two 50 N bowling balls 1 m off the floor?

6. The unit for power is called a watt.
Power is the rate at which work is done.
Power = Work / time
The unit for power is called a watt.

7. There are 6 types of simple machines that help make work easier.
Work and Machines
There are 6 types of simple machines that help make work easier.
Lever Screw
2. Inclined Plane 5. Pulley
3. Wedge Wheel and Axle

8. Work and Machines Vocabulary
Input force - the amount of force you must put into the machine.
2. Output force - the amount of force you get out of a machine.
Fulcrum - the fixed point that acts as a pivot.
Load - same as the output force. It is usually what you are trying to move.

9. There are 3 classes of levers.
Work and Machines
Lever
A lever is a simple machine that consists of a bar that pivots at a fixed point, called a fulcrum.
There are 3 classes of levers.

10. Work and Machines 1st Class Lever
The fulcrum is between the input force and the load.
These levers are used to increase force or increase distance.
Examples include a seesaw, scissors, and pliers.

11. Where would the fulcrum and the load be in a seesaw?

12. Examples of class 1 levers
Work and Machines
Examples of class 1 levers
see-saw
hammer's claws
scissors
pliers
1st Class Lever

13. Work and Machines 2nd Class Levers
The load is between the fulcrum and the input force.
They do not change the direction of the input force, but they do allow you to apply less force than the force exerted by the load.
Examples include a wheelbarrow and a nutcracker.

14. Where is the fulcrum, input force and load on a wheelbarrow?

15. Work and Machines 2nd Class Lever Examples stapler bottle opener
wheelbarrow
nail clippers
nut cracker
2nd Class Lever

16. Work and Machines 3rd Class Levers
The input force is between the fulcrum and the load.
They increase the distance through which the output force is exerted.
Examples of these are baseball bats, your bent arm, and fishing rods.

17. Where is the input force, output force, and fulcrum when using a baseball bat?

18. Number of Class 3 Levers Used
Work and Machines
3rd Class Levers
Item
Number of Class 3 Levers Used
fishing rod
a single class 3 lever
tweezers
Two class 3 levers
tongs

19. Inclined Planes
An inclined plane is a simple machine that is a straight, slanted surface.
Inclined planes use a longer distance to exert a smaller force.

20. Work and Machines Wedge A wedge is a double inclined plane that moves.
- Examples include doorstops, ax heads, and knives.

21. Work and Machines Screws
A screw is an inclined plane wrapped around a cylinder.
Examples include a screw, jar lid, soda bottle caps

22. Work and Machines
Pulleys
A pulley is a machine that consists of a grooved wheel that holds a rope or a cable.

23. Work and Machines Pulleys
A load is attached to one end of the rope, and an input force is applied to the other end.
Examples include flagpoles, sailboats, blinds, and curtain rods.
There are two types of pulleys- fixed and moveable.

24. Work and Machines Fixed Pulleys
A fixed pulley has been attached to a stationary, or fixed, object.
Fixed pulleys change the direction of the force, but they do not increase force.

25. Work and Machines Fixed pulleys
You can use fixed pulleys to pull down on a rope to lift up the object.

26. Work and Machines Moveable Pulleys
Moveable pulleys increases the force without changing the direction of the force.
The input force must be exerted over a greater distance than load is moved.

27. The moveable pulley is attached to the object being moved.
Work and Machines
Moveable Pulleys
The moveable pulley is attached to the object being moved.

28. Work and Machines
Wheel and Axle
A wheel and axle is a simple machine consisting of two circular objects of different sizes.
The wheel is the bigger circle, while the axle is the smaller of the two.

29. Work and Machines
Examples of wheel and axles are doorknobs, wrenches, and steering wheels.

30. Work and Machines Most machines that we use are compound machines.
Compound machines are made of two or more simple machines.