Energy, work and Power Focus Lesson Name__________________________

Energy can be either kinetic energy (energy of motion) or potential energy (stored energy of position). Objects have mechanical energy if they are in motion and/or if they are at some position relative to a zero potential energy position (for example, a brick held at a vertical position above the ground or zero height position). A moving car possesses mechanical energy due to its motion (kinetic energy). A moving baseball possesses mechanical energy due to both its high speed (kinetic energy) and its vertical position above the ground (gravitational potential energy).

Potential Energy

1. Find the potential energy of a body of mass 5Kg and is 25m above from the ground?

2. What is the gravitational

potential energy of a 150kg object suspended 5m above

the earth’s surface?

Word Formula Definition

Work

Power

Mechanical Energy Ep=

Ek=

3. What is the gravitational potential energy of a 2.5kg object that is 300m above the surface of the earth?

Kinetic Energy

4. What is the kinetic energy of a 25kg object moving at a velocity of 5m/s?

Total Mechanical Energy (Kinetic + Potential Energy)

5. A piece of paper is at rest on the shelf with 30 J of potential energy. A gust of wind knocks it off the shelf and gives it 20 J of kinetic energy. What is the total mechanical energy of the paper?

6. A toy is on the ground at rest with 0 J of potential energy. A child does 10 J of work to lift it up to a 1 meter high shelf. What is the total mechanical energy on the toy?

7. Using the graph below answer the questions about A through D:

8.

__________________________________________________________________________________________________

9. What does this mean?

__________________________________________________________________________________________________

10. What makes the first energy system renewable?

11. Why is the second energy system non-renewable?

Name the energy transformations from:

12. apple to bicyclist __________to ________

13. gasoline to car __________ to _________

14. sun to plants __________ to __________

15. cord to appliance __________ to _______

16. Classify the forms of energy listed below as potential or kinetic.

Work

17. An ant sits on the back of a mouse. The mouse carries the ant across the floor for a distance of 10 m.

Was there work done by the mouse? Explain.

18. You lift a 45-N bag of mulch 1.2 m and carry it a distance of 10. m to the garden. How much work was

done?

19. A 50 kg gymnast jumps upward a distance of 0.50 m to reach the uneven parallel bars. How much work

did she do before she even began her routine?

20. A people-moving conveyor-belt moves a 600-N person a distance of 100 m through the airport.

i. How much work was done?

ii. The same 600-N person lifts his 100-N carry-on bag upward a distance of 1 m. They travel another

10 m by riding on the “people mover.” How much work was done in this situation?

Power21. A motor does 5,000 joules of work in 20 seconds. What is the power of the motor?

22. A machine lifts a 200 kg rock 6 meters above the ground in 30 seconds. What is the power of this

machine?

23. A toaster oven uses 67,500 joules of energy in 45 seconds to toast a piece of bread. What is the power of

the oven?

24. A 500 kg suitcase got lifted up 3 meters onto a conveyer belt which took 5 seconds. Calculate power.

25. Allen lifts his weight (50 kg) up a staircase that is 5 meters high in 30 seconds. How much power does

he use?