1. 5.3—Simple Machines

2. Simple machine = a machine that does work with only 1 movement
6 types:

3. 1. Lever = a bar that is free to pivot (turn)
1. Lever = a bar that is free to pivot (turn) about a fixed point called the fulcrum. From the fulcrum to where the effort force is applied is called the effort arm. From the fulcrum to where the resistance force is applied is called the resistance arm.

4. First-class lever—the fulcrum is between
First-class lever—the fulcrum is between the effort force and the resistance force. It may multiply force and always changes the direction of the applied force. The fulcrum does not need to be in the exact center.

7. b) Second-class lever—the resistance
b) Second-class lever—the resistance force (load) is between the effort force and the fulcrum. It multiplies force (but does not change the direction)
l effort arm l
l-resist. arm-l

9. c) Third-class lever—the effort force is
c) Third-class lever—the effort force is between the resistance force and the fulcrum. It cannot multiply force because the effort arm is shorter than the resistance arm. It increases the distance over which the resistance force is applied (and does not change the direction)

10. l-----resistance arm-----l
l---effort---l
l-----resistance arm-----l

13. For an ideal lever, the ideal mechanical advantage, IMA, is
IMA = Length of effort arm Length of resistance arm
= Le Lr

14. 1st Class: fulcrum in center
2nd Class: load in center
3rd Class: effort in center

15. 2. Pulley = a grooved wheel with a rope, chain, or
2. Pulley = a grooved wheel with a rope, chain, or cable running along the groove. Some change the direction of the effort force; some also multiply the effort force. A pulley is a modified lever—the center of the pulley is the fulcrum; the two sides are the effort and resistance arms.

16. a) Fixed pulley—1 pulley that is. attached to a fixed object
a) Fixed pulley—1 pulley that is attached to a fixed object. The lengths of the effort and resistance arms are the same. The effort force is not multiplied, so the IMA = 1.
Resistance
Arm
Effort
Arm

18. b) moveable pulley—one end of the
b) moveable pulley—one end of the rope is fixed and the pulley is free to move. The force is multiplied by 2 (IMA = 2). The (length of the effort arm) = 2 x (length of resistance arm).

19. The rope has to be pulled
twice as far as the object
moves, so IMA = 2

20. c). Block and tackle (sometimes called a compound
c) Block and tackle (sometimes called a compound pulley)—two or more fixed and moveable pulleys. The force is multiplied by the number of resistance rope segments, so IMA = number of resistance rope segments.
You don’t count the rope that you pull, only the rope segments supporting the load.

21. IMA = IMA = 4
Left: person exerts half as much force as without the pulleys.
Right: person exerts one-fourth as much force.

22. IMA = 4
100 pounds being pulled by 4 lines divides the weight by 4.

23. 1: IMA = 1 (Fe = Fr; just a simple fixed pulley)

24. Because the IMA increases, you have to pull farther on the rope—twice as far as the object moves when the IMA is 2, 4 times as far when the IMA is 4.

25. 3. Wheel and axle = a machine. consisting of 2 wheels that rotate
3. Wheel and axle = a machine consisting of 2 wheels that rotate together; the smaller (radius) of the 2 wheels is the axle; the wheel is sometimes a handle; a modified lever.
IMA = radius of wheel = rw
radius of axle ra

28. Gears = wheels with interlocking teeth around their circumferences
Gears = wheels with interlocking teeth around their circumferences. When one wheel turns, the teeth force the other wheel(s) to turn. The wheels are usually different sizes. If they are, then the larger gear is the wheel (effort gear). The smaller gear is the axle (resistance gear); it turns many times for each turn of the wheel.
A special type of
wheel and axle.

30. 4. Inclined plane = a sloping surface that reduces the amount of force required to do work by increasing the distance; includes ramps, stairs, ladders, etc.
IMA = effort distance =
resistance distance
IMA = length of slope = l
height of slope h

32. IMA = l/h

34. 5. Screw = an inclined plane wrapped in a spiral
5. Screw = an inclined plane wrapped in a spiral around a cylindrical post. A screw is a type of inclined plane that moves through the object rather than the object moving (so a spiral ramp is not a screw because it does not move). The direction of the force is changed from circular to linear.

36. 6. Wedge = an inclined plane with one. or two sloping sides
6. Wedge = an inclined plane with one or two sloping sides. A wedge is a type of inclined plane that moves through the object rather than the object moving. A wedge changes the direction of the effort force.

39. Compound machine = 2 or more simple machines used together.
Most machines are actually compound machines.