Use DUFAS to Solve1. One of the tallest radio towers is in Fargo, North Dakota. The tower is 629 m tall, or about

44 percent taller than the Sears Tower in Chicago. If a bird lands on top of the tower, so

that the gravitational potential energy associated with the bird is 2,033 J, what is its

mass?

2. A table tennis (ping-pong) ball has a mass of about

2.45 kg. Suppose the ball is hit across the table with a velocity of about 4.0 m/s. What is its

energy?

3. Mr. Madigan holds a 4.45kg bowling ball out a window. Just before Mr. Madigan releases the bowling ball, the bowling ball has 21.0J of

gravitational PE with respect to the ground. How high is Mr. Madigan’s arm above the ground, in

meters?

.329 kg

19.6 J KE

.481 meters

Energy Review

1. Fill in the units for A-L:

A. Mass= Kg B. Force= N C. Velocity= m/s

D. Height= m E. Distance= m F. GPE= J

G. Acceleration of Gravity= m/s2 H. KE= J

• Work= J J. Power= Watts K. EPE= J

L. Time= s

2. F = 400 Nd = 0 mW = ? J

W = F*d

= 400N * 0m = 0J

There was NO work done b/c the truck never moved! = a distance of 0m.

3. d = 13mF = 23NW = ? J

W = F*d

= 23N * 13m = 299J

4.h = 470mm= 62kgg = 9.8 m/s2

PE = ? J

PE = mgh

= 62kg * 9.8m/s2 * 470m

= 285,572 J

5.v = 2m/s KE =

½ m * v2

KE = ? J

m = .01 kg

= .005 kg * 4 m2/s2 = .02 J

6. v = 2.8 m/s KE = 1/2m*v2

m = 40 kgKE = ? J

= 20 kg * 7.84 m2/s2 = 156.8 J

7.

1.3kg280JH=PE/(gm)

280J/1.3kgx9.8m/s2

h= 21.97m

10-14

.11

10.ME 11.EE 12.KE 13.PE 14.KEHeat/Friction is given off at point the turbines

.14

.11

.10.12

.13

15. k= 6000N/mX= .25mEPE=1/2kx2

(6000N/m) x (.25m)2

23000N/m x .0625m2

EPE =187.5 J

Elastic Potential Energy

19. Height affects GPE the most!

20. Friction: A force that opposes the motion between two objects in contact with each other. (always oppositional forces)Gravity is an attraction that acts between any two objects that have a mass. (the two masses aren’t always touching each other)

21. Levels of PE and KE at different positions on a ramp:

A. PE is max. & KE 0 J

B. PE is high & KE is low

C. KE = PE

D. PE is low & KE is high

E. PE is min & KE is max.

22. Mechanical and Electromagnetic waves do not transport matter but rather

23. We get sunburned at the beach because our skin absorbs the UV rays from the sun. When we use sun screen, it helps to reflect the harmful UV rays so that our skin does not absorb them.

energy

25.

Position 1 2 3 4 5

Total Energy

1960 J

1960 J

1960 J

1960 J

1960 J

Potential

Energy

1960 J

980 J 0 J 980 J1960 J

Kinetic

Energy

0 J 980 J1960 J

980 J 0 J

26. Power= Work / time1700J / 900sec

= 1.88 watts27. The Law of Conservation of Energy states that energy cannot be created or destroyed but it can be transformed or transferred.

28. The orange that is more massive has more gravity pulling on it b/c it has more mass.

32. Velocity affect KE the most!

33. Mechanical waves travel faster through more dense mediums (solids & liquids) because the particles are closer together and are able to transfer the energy from one particle to another faster.

34. Electromagnetic Spectrum

Radio Microwave IR

Visible

UV X-rays gamma

LowFrequency

HighFrequency

35. Infrared E Requires a medium to travel through.

Visible I Does not require a medium to travel through.

Microwaves H Are used by doctors to determine if a bone is broken or not.

Ultra violet

F Have the shortest waves and are used by doctors to kill cancer cells in humans.

Mechanical waves

G Have the longest waves and are used for stereo’s.

Gamma B This is the only part of the spectrum that humans can see light in.

Radio D These are the harmful rays from the sun that causes sunburn and skin cancer.

X-rays A Military uses these waves to see the heat waves at night.

Electromagnetic wave

C They are used to help heat up our food in our homes. They are also used in Doppler radar too!

*38-40.

38. How much GPE is in this system? 39. How much KE is there in this system at the midpoint? 40. What is the Total Energy (TE) of this system?

100J

100J

50 J

What to Study to be Successful?

Review quiz (re-work problems you got wrong)Review all handouts and RFA pages. Review calculations worksheet. Work different problems so you know how to do them for tomorrow’s exam.

Look over review packetE-mail me any questions or see me before your exam tomorrow.Study in chunks of timeQuality vs. Quantity studyQuick review in the AMGood Luck!

Flash CardFlash card for exam= no formulasOnly material you don’t know wellMay use both sidesCan’t forget notecardName MUST be on it.STUDY FIRST BEFORE YOU DO THE NOTECARD!

Bowling Ball Drop• Did the bowling ball and volley ball hit the ground at the same time?

• What do you think caused the volley ball to not hit the ground at the same time as the bowling ball?Answer* Air resistance slowed the volley ball down more so than the bowling ball because it has less mass!

How to prepare for the Energy

Exam• Review Quizzes (redo problems)• Review Notes and Handouts (*’s, underlined)• Review RFA’s• What was important in the Labs?• Redo DUFAS problems (you have the answers already)

• Know what you have to Review or Study• Quizlet• Review Packet Last ( this is NOT enough)