Discussion. 1. What is a simple definition of a machine? What is a more technical definition?

1. What is a simple definition of a machine? What is a more technical definition? What does this definition imply?

2. Describe some very simple machines. What are some complex ones? Give examples of your own.

3. What are the output and input of a machine?

4. What are the machines called whose input is a natural source of energy? What are some natural sources of energy and the machines that use them?

5. Why aren't electric motors prime movers?

6. What is force in a technical sense? Give some examples.

7. How can work be expressed mathematically? Give an example.

8. In what way must a force be acting to produce work? Give examples. What kind of effort would not produce work?

9. What are the two principal kinds of motion?

10. Which kind of motion is reciprocating motion? What is its principal characteristic?

1l. What is torsion? What is necessary to produce it? What is necessary to produce rotary motion?

12. What is an important problem in many machines? Give an example.

13. Why is no machine 100% efficient?

14. What are some other reasons why energy is never completely utilized?

15. How do mechanical engineers deal with the factor of friction?

16. What is the ratio between a machine's output and input? Give an example.

17. In a technical sense, what does power define? Give an example.

18. How is the rate of doing work usually given in the En­glish-speaking countries? Why was the term invented? What does it equal?

19. In what terms is power measured in the metric system?

20. What do the joule, the watt, the kilowatt, and the Newton approximately equal in the English system?

21. Why can the terms watt and kilowatt be used to refer to mechanical as well as electrical energy?

Review

A. Match the terms on the left with the statements on the right.

1. Force a) The ratio between output in work and input in energy.

2. Work b) The resistance to motion produced by two bodies those are moving in contact with each other.

3. Machine c) Motion in a straight line, or linear motion.

4. Prime Mover d) An English measure of power equal to 33,000 foot-pounds per minute.

5. Translation e) A twisting force that produces torsion or rotary motion.

6. Reciprocating f) The ratio of output force to input force Motion of a machine.

7. Rotary Motion g) A metric measure of power, equal to one joule per second.

8. Torque h) An English measure of work, a force of one pound moving through a distance of one foot in the direction of the force.

9. Efficiency i) An effort that results in motion or physical change.

10. Mechanical Advantage j) Force necessary to move one kilogram one meter per second.

11. Friction k) Force times the distance through which it is exerted.

12. Power l) A metric measure of energy, equal to approximately % of a foot-pound.

13. Foot-pound m) A device that applies force to accomplish an objective.

14. Horsepower n) The strength or force at which work is performed.

15. Joule o) A machine that converts energy from a natural source.

16. Watt p) A metric measure of power, equal to a thousand watts, or approximately in the English system.

17. Kilowatt q) Motion in a circular path.

18. Newton r) Back and forth or up and down motion in a straight line.