1. Simple Machines
5.2

2. SIMPLE MACHINES: ease load, changing either magnitude or direction of a force
WORK input<WORK output
FORCE exerted<FORCE machine
LEVER
Simple Lever
Pulley
Wheel and axle
INCLINED PLANE
Simple Inclined Plane
Wedge
Screw

4. The Lever Family! EXAMPLES Claw hammer Crowbar See-saw
A bar that is free to pivot or turn at a fixed point.
-Fixed point=Fulcrum
-Input Arm=Distance from the fulcrum to where the input force is.
-Output Arm=distance from the fulcrum to the output force.

5. Three classes
1st class lever: Claw hammer, the fulcrum is located in the middle of the arm.
2nd class lever: The fulcrum is located at the end of the arm, output force is b/t input force and fulcrum: A wheelbarrow.
3rd class lever: The fulcrum is located at an end of the arm, the input force is applied b/t the output force and fulcrum.

8. Pulleys Pulleys are modified levers.
Fixed Pulley-change direction of the input force
Movable Pulley- increase input force.
Axel = Fulcrum
Depending on the number and arrangement of pulleys, the mechanical advantage is different.
Fr=Fe Mechanical Advantage =1 w/ 1 fixed pulley

9. Block and Tackle-System w/ fixed and movable.

11. Wheel and Axle
Axle in the center of the wheel

12. Inclined planes Inclined planes - multiply and redirect forces. Wedge
- is a modified inclined plane
Screw
- is an inclined plane wrapped around a
cylinder.

14. Compound Machines
Two or more simple machines

15. Using Machines INPUT FORCE-Force applied to the machine
Increase Force
Change Direction
Make Work Easy
INPUT FORCE-Force applied to the machine
OUTPUT FORCE-Applied by the machine
Mechanical Advantage= Ratio Output Force/Input Force
Fresistance/Feffort

16. Efficiency (%) = Output Work/Input Work x 100%
Ideal Mechanical Advantage (IMA)=equal to the displacement of the effort force divided by the displacement of the load.
Fr/Fe=de/dr
Efficiency (%) = Output Work/Input Work x 100%
MA/IMA x100

17. Practice Problem:
1.) You examine the rear wheel on your bicycle. It has a radius of cm and has a gear with a radius of 4 cm. When the chain is pulled with a force of 155 N, the wheel rim moves 14 cm. The efficiency of this part of the bicycle is 95%.
A. What is the IMA of the wheel and gear: 4 cm/35.6 cm=0.112
B. What is the MA of the wheel and gear: e=ma/IMAx 100
MA=e/100 xIMA (95/100) 0.112= 0.106
C. What is the resistance force: MA=Fr/fe Fr=Max Fe 0.106(155)=16.4
D. How far was the chain pulled to move the rim 14 cm: IMA=de/dr de=IMA x dr (14)=1.57 cm

18. 2. A sledgehammer is use dto drive a wedge into a log to split it
2. A sledgehammer is use dto drive a wedge into a log to split it. When the wedge is driven 0.2 m into the log, the log is separated a distance of 5 cm. A force of N is needed to split the log and the sledgehammer exerts a force of
What is the IMA of the wedge?
(4)
What is the MA of the wedge?
(1.5)
Efficiency?
(38%)

19. Impulse
Average force times time Ns
F=ma….

20. Momentum Mass times velocity Kg m/s Vector Impulse Momentum Theorem
Impulse is the change in p
CONSERVATION OF MOMENTUM:
pi=pf