Work and Machines s1

WORK AND MACHINES Use pages 98 – 126 in your textbook to answer these questions. 1. Give an example of how you can exert a force and do no work. When you carry your books to school are you doing work? force with no movement equals no work; No, no movement in the direction of your force. 2. If you move a box 200 meters with a force of 10 N how much work did you do? J = N x m, so… 10 N x 200 m = 2000 J 3. What is the definition of a machine? What are the 3 ways machines make work easier to do? machines make work easier to do. change force, distance or direction 4. What is input force? What is output force? what you do; what the machine does 5. What is the mechanical advantage of a machine whose output force is 60 N and input force is 30 N? What is the mechanical advantage of a machine that only changes the direction of force (for example: a fixed pulley)? MA = output force / input force, so… 60 N/30 N = 2; MA = 1 6. What is the efficiency of a machine whose output work is 100 J and input work is 1000 J? Why is efficiency always less than 100%? efficiency = output work / input work x 100%, so… 100 J/ 1000 J x 100% = 10% 7. How does friction affect mechanical advantage? Which machine is more efficient, the incline plane or the lever? decreases MA; lever 8. Name the six simple machines. What are the two “parent” simple machines? incline plane, lever, wedge, wheel & axle, pulley, screw; incline plane, lever 9. What is the ideal mechanical advantage of a incline plane with length 12 meters and height 6 meters? MA = length of ramp/ht. of ramp, so… 12 m/ 6 m = 2 10. Draw pictures below of the 3 classes of levers. Label the input force, output force, and the fulcrum. (Draw the pictures on the back of this paper) see page 115 in book 11. What is the ideal mechanical advantage of a lever whose distance from the fulcrum to the input force is 100 meters and whose distance from the fulcrum to the output force is 10 meters? MA = input lever length/ output lever length, so… 100 m/ 10 m = 10 12. What is the ideal mechanical advantage of a wheel and axel whose wheel radius is 10 meters and axle radius is 1 meter? MA = wheel radius/ axle radius, so… 10 m/ 1 m = 10 13. What are the three types of pulleys? How do you find the ideal mechanical advantage of a pulley? As you increase the mechanical advantage of a pulley you also increase the ______that you must pull. fixed, moveable, system; MA = number of sections of work supporting weight; distance 14. What are compound machines? What are gears? 2 or more simple machines working together; toothed wheels that fit each other 15. Do muscles push or pull? What are tendons? Give examples of three classes of levers in the human body. What kind of machine are your incisors like? pull; connect muscles; neck first class, arm 3rd class, ball of foot 2nd class, wedges