1. in Mechanical Systems, Work Is Done When What?

Name ______Period ______

Reading Guide 2.1

1. In mechanical systems, work is done when what?

2. Write the equation for work and tell what each letter stands for.

3. In the English system, work is measured in ______.

4. In the SI system, work is measured in what 2 units?

5. The distance and direction through which an object moves are also called it’s what?

6. Explain the difference between positive work and negative work.

7. Look at Example 2.1 then solve the following.

Find the amount of work done by a weight lifter in lifting a 520 Newton barbell a

distance of 4 meters.

8. Why is no work done on the barbell while the weight lifter hold it in place above his head?

9. What “biological work” is being done while holding a barbell?

10. Look at example 2.2. Why is the answer negative?

11. When you throw a ball you do work. If you were to determine the magnitude of the work you do(W=Fd), what distance would you use, the distance your hand went during the throw, or the distance the ball lands away from you?

12. When the weight lifter does work on a barbell, the gravitational potential energy gained by the barbell equals what?

13. When brakes slow down a car, the car loses kinetic energy. The amount of kinetic energy lost equals what?

14. Machines are designed to do what?

15. Output work is always ______than input work.

16. Give an example of something that causes undesired but unavoidable losses of energy.

17. Efficiency is a ratio of

18. Output work is work done by what?

19. Input work is work done on what?

20. Write the formula to calculate percent efficiency

21. Look at example 2.3 and then solve the following.

Given: A block and tackle is used to lift an engine. The engine weighs 700 N and is moved 1.5 m. The operator pulls with a force of 120 N over a distance of 10 m.

Find Work Input.

22. From #21, find Work Output.

23. From #21, find the efficiency of the system in a percent.