Name: ________________________________

Energy Transfer ModelENERGY “Cheat”sheet

Symbol Type of Energy When is this energy present? Equation Notes

Physics! / Unit VII / ETM

– 1 – from Modeling Workshop Project © 2006

Worksheet 3: Force vs Displacement Graphs

17. Suppose in the spring lab, one group found that Fspring = (1000 N/m)(∆x). Construct a graphical representation of force-vs-displacement. (Hint: make the maximum displacement 0.25 m.)

Graphically determine the amount of energy stored while stretching the spring from x = 0 cm to x = 10 cm.

Graphically determine the amount of energy stored while stretching the spring from x = 15 cm to x = 25 cm.

18. The graph below was made from data collected during an investigation of the relationship between the amount two different springs stretched when different forces were applied.

For each spring, determine the spring constant.

For each spring, find the amount of force required to stretch the spring 3.0 m.

For each spring, find the Us stored when stretched 3.0 m.

Determine the amount that Spring A needs to be stretched in order to store 24 joules of energy.

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Spring A

Spring B

1 2 3 4 5 6 7 8x �m �

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10

15

20

25

30

35

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Physics! / Unit VII / ETM

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Energy Test Review Packet

Name:_________________ Period:_____________ Date:________________________

19. A brick falls (starting with a speed of 2 m/s straight down) from a height of 10 meters. How much work does the Earth do on the brick while it falls?

20. The same brick is tossed (with the same initial speed of 2 m/s) at an angle of 34º from a height of 10 m. How much work does the Earth do on the brick from the instant it leaves the hand until the instant it is about to touch the ground?

21. A block, sliding across a table, runs into a spring (that is secured at the other end to the wall). The block compresses the spring (ks = 15 N/m) by 25 cm. How much work does the spring do on the block?

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from Modeling Workshop Project © 2006 ! – 10 –

Worksheet 4: Problem Solving

22. A 500-kg pig is standing at the top of a muddy hill on a rainy day. The hill is 100.0 m long with a vertical drop of 30.0 m. The pig slips and begins to slide down the hill. What is the pig’s speed at the bottom of the hill?

23. A 60 kg student jumps from the 10 meter platform at UD’s swimming complex into the pool below.Once you’ve analyzed that situation, see what would be different if the student massed 75 kg instead of 60 kg.

Physics! / Unit VII / ETM

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24. A 500 g block is pushed down on a spring, compressing it 0.30m.

Initial Final

v=0 y=0

y=?m=500 gk=100 N/m

!x=0.30 m

25. A 24 kg child descends a 5.0 m high slide and reaches the ground with a speed of 2.8 m/s.

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from Modeling Workshop Project © 2006 ! – 12 –

26. A 0.500 kg block attached to a spring with length 0.60 m and spring constant 40 N/m is at rest with the back of the block at point A on a very low-friction, horizontal table. You pull the block to the right along the surface with a constant horizontal force of 20 N. When the back of the block reaches point B, you let go of the block.

27. The Great Puffini is an 80-kg circus performer who is shot from a cannon (actually a spring gun). You don’t find many men of his caliber, so you help him design a new gun. This new gun has a very large spring with a very small mass and a spring constant of 1100 N/m that he will compress with a force of 5500 N. The inside of the gun barrel is coated with Teflon, so the average friction force will be only 40 N during the 5.0 m he moves in the barrel. At what speed will he emerge from the end of the barrel, 3.5 m above his initial rest position (3.5 m would be his vertical displacement as he travels along the barrel)?

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Worksheet 5: PowerSome space for notes about power:

28. A 60 kg box is lifted by a rope a distance of 10 meters straight up at constant speed. How much power is required to complete this task in 5 seconds?

29. Hulky and Bulky are two workers being considered for a job at the UPS loading dock. Hulky boasts that he can lift a 100 kg box 2 meters vertically, in 3 seconds. Bulky counters with his claim of lifting a 200 kg box 5 meters vertically, in 20 seconds.To which worker would you give a greater power rating?

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from Modeling Workshop Project © 2006 ! – 14 –

30. A 1994 Ford Mustang is driving down a road with a constant speed of 30 m/s. The engine must exert a 5000 N force to maintain this speed.a. How powerful is the engine (answer in Watts)?

b. How does the Mustang's power rating compare to the 220 hp Dodge Stealth engine (1 hp = 746 W)?

31. The trains on the Viper are raised from 10 m above ground at the loading platform to a height of 60 m at the top of the first hill in 45 s. Assume that the train (including passengers) has a mass of 2500 kg. Ignoring frictional losses, what power motor would be required to accomplish this task?

32. Your electric utility company sends you a monthly bill informing you of the number of kilowatt-hours you have used that month.a. Is the utility charging you for energy or power? Explain.

b. How many joules of energy does your 1600W blow drier require if you dry your hair in 5 min?

Physics! / Unit VII / ETM

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Physics! / Unit VII / ETM

from Modeling Workshop Project © 2006 ! – 16 –