1. Jillian Pardini & Hank Finch
Work and Machines
Jillian Pardini & Hank Finch

2. Machines
A machine is a device that changes a force and makes work easier to do. Machines change the size of a force needed, the direction of a force, or the distance over which a force acts. Machines make things easier by accomplishing one or more of the following;
Transferring a force from one place to another
Changing direction of a force
Increasing the magnitude of a force
Increasing the distance or the speed of the force

3. Simple machine examples
Inclined plane
Screw
Pulley
Wheel and Axle
Wedge
Lever

4. Increasing Force
If a machine increases the distance in which you exert a force, then it decreases the amount of force needed to exert. Lifting something one at a time takes less force but you travel a greater distance.

5. Increasing Distance
A machine that increases the distance in which you exert a force increases the amount of force required. To row a boat you pull the oar a short distance to move the other end a large distance. This in turn requires you to exert a greater force.

6. Work Input & Output Work Input Work Output
Input force is the force you exert on a machine. The distance a force travels is input distance. The work done on the input and travels through the input distance is work input. Work input force equals the input force multiplied by the input distance.
The force that is exerted by a machine is called the output force. The distance the output is exerted through is the output distance. All machines use some amount of input work to overcome friction.

7. Friction
When rowing a boat work is done on the oar which in turn do work on the water to move the boat. As rowers pull in one end of each oar the other end pushes against the water. The force of the oar in the water causes an equal and opposite reaction force to be exerted by the water on the oar. Although due to friction, the work done by the machine is always less than the work done on the machine so you can never get more work out than you put in.

8. Quiz Time

9. 1. When a machine does work on an object the output work is…
Always less than the input work
Always equal to the input work
Always greater than the input work
Sometimes equal to the input work

10. 2. A machine can do any of the following except…
Increase distance
Increase work
Increase force
Change direction

11. 3. The force that causes objects to slow down or stop is…
Work
Force
Friction
Direction

12. 4. A inclined plane is an example of…
Increasing force
Increasing distance
Changing direction
Friction

13. Resistance Power Effort Work
5. The transfer of energy that occurs when a force makes an object move…
Resistance
Power
Effort
Work

14. 6.The rate at which work is done…
Force
Efficiency
Power
Effort

15. 7. Simple machines make work easier by trading ________ for force.
Distance
Motion
Friction
Work

16. 8. How does a ramp make lifting a heavy object easier?
The object is moved over a shorter distance
The ramp increases the amount of work you do
Less force is needed to move the object over a longer distance
More force is needed to move the object over a longer distance

17. Give an example of a simple machine and what it could be used for.
Extra Credit:
Give an example of a simple machine and what it could be used for.

18. Answers A B C D