1. Chapter 11 work and machines

2. Anytime that you exert a force and cause an object to move in the direction of the applied force you do _________. work

3. In which of the 4 scenarios is work being done on the object?

4. How much work is done when a 10N box is moved a distance of 2 meters? Work = force x distance W = 10 N x 2 m W = 20 J

5. What is the power of a machine that does 20 J of work in 10 seconds? Power = work time Power = 20 J = 2 watts 10 s

6. Devices that allow you to do work in an easier way are ___________ machines

7. When you do work, the force you exert is called the ___________ force.

8. The push or pull that is being done by the machine is the __________ force. Output

9. The number of times a machine increases a force exerted on it is called ____________ ____________. Mechanical advantage

10. What is the mechanical advantage of the pulley system below where Wilbur inputs 100N to pull up a 4000N tank? MA = output force input force MA = 4000N = 40 100N

11. The efficiency of a machine compares output work to input work and is expressed as a percentage. Our cars are only about 30% efficient. Machines, like cars, become more efficient when _________ is reduced. friction

12. What is the efficiency of a machine in which 200 J of work are put in but only 100 J of work come out? 200J 100 J Efficiency = output work x 100 = input work 100 J x 100 = 50% 200 J Work input Work output

13. A twisted inclined plane is a ______. screw A bar that pivots about a fixed point is a _______. lever A grooved wheel with a rope wrapped around it is a _________. pulley Two inclined planes put together make up a ________. wedge

14. What is the mechanical advantage of an inclined plane that is 4 meters long and 2 meters high? MA = ramp length = ramp height 4 m = 2 2m

15. If the MA of this lever is 3, what effort(input) force will lift the 150 N Load? MA = output force = input force 150 N = 3 input force = 50N Input force

16. What is the mechanical advantage of the following pulley systems? = # ropes that pull up on the load

17. What is the mechanical advantage of the wheel and axle? MA = radius of the wheel radius of the axle MA = 5 = 5 1

18. How can you increase the mechanical advantage of this lever? Move the fulcrum closer to the stone, increase the length of the effort arm

19. Wedge thickness = 3 m 2m 1 m The wedges below are all 6 m long. What is the mechanical advantage of each wedge? MA = wedge length wedge height MA = 6m = 26m = 36m = 6 3m 2m 1m