6 2012 ppt batfink energy review

I’M FULL OF ENERGY

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Stating the ProblemThe Batallac, the 1500 kg car used byBatfink and Karate to fight crime, is stopped at a height of 35 meters at the top of a damaged bridge. You may assume there is no friction. How much energy has been transferred? What container is this energy stored in? Remember that Batfink is 50 kg and Karate is 150 kg.

SOLUTION:

K U E

How much energy has been transferred into which container?

m = 1700 kg Ug

g = 9.8 m/s2

Δy = 35 m

Ug = 583,100 J

F = -kΔlP = W/t

Working the Problem

What is the velocity of

the Batallac just before

it hits the water?

SOLUTION:

K U E

Final velocity.

m = 1700 kg Vf

mb = 25 kgΔy = 35 m Ug = 583,100 J

Vf= 26.19 m/s F = -kΔlP = W/t

Stating the Problem

Our heroes, Batfink and Karate, arestuck in quick drying cement. BigEars Ernie has vertically displaced aone metric ton (1,000 kg) wreckingball 4 meters and is attempting tosmash them. How much energy isbeing stored in the g-field?

SOLUTION:

K U E

Find energy.

m = 1000 kg Ug

Δy = 4 m g = 9.8 m/s2

Ug= 39,200 J

Working the Problem

Draw an energy bar chart to illustrate the distribution ofenergy when the wreckingball is displaced 3 meters atthe opposite end of it’s swing.

SOLUTION:

K U E

Distribution of energy containers.

ET = 39,299 J KEm = 1000 kg Δy = 3 m g = 9.8 m/s2

KE= 9,800 J

Energy Bar Chart

Total Energy Ug KE0

5,000

10,000

15,000

20,000

25,000

30,000

35,000

40,000

45,000

What was the force exerted on the wrecking ball to place it in its original position?

Stating the Problem

SOLUTION:

K U E

Find force.

m = 1000 kg FΔy = 4 m g = 9.8 m/s2

F= 9,800 N

Stating the Problem

The Batallac has come to a stop between the two bridge decks 81.87 meters above the icy river. What is the total energy in the gravitational field?

SOLUTION:

K U E

Find energy.

m = 1700 kg Ug

Δy = 81.87 m g = 9.8 m/s2

Ug= 1,363,954.2 J

Stating the Problem

What is the maximum velocity the batallac will attain before hitting the water?

SOLUTION:

K U E

Find velocity.

m = 1700 kg vΔy = 81.87 m g = 9.8 m/s2

Ug= 1,363,954.2 J

v = 40.06 m/s

Stating the Problem

How much time would it take for the batallac to reach the water below?

SOLUTION:

K U E

Find time.

vi = 0 m/s tf

vf = 40.06 m/s Δy = 81.87 m g = 9.8 m/s2

tf= 4.09 s

Stating the Problem

Fortunately, Batfink is able to free himself from the Batallac and stop the car from falling into the river. How much force was needed to bring the car to a complete stop?

SOLUTION:

K U E

Find force.

m = 1700 kg FΔy = -81.87 m g = 9.8 m/s2

Ug= 1,363,954.2 J

F = -16,660 N

Stating the Problem

If this force was applied during the entire fall of the Batallac, how much power did Batfink exert?

SOLUTION:

K U E

Find power.

m = 1700 kg PΔy = 81.87 m g = 9.8 m/s2

Ug= 1,363,954.2 JTf = 4.09 s P = 333,485.13 W

Stating the Problem

Batfink is dropped through a trap door disguised as a welcome mat. If he falls 20 meters, what is his KE just before hitting the ground?

SOLUTION:

K U E

Find energy.

m = 50 kg KEΔy = -20 mg = 9.8 m/s2

KE = -9,800 J

Stating the Problem

Fortunately for Batfink, there was a spring on the floor under the trap door. If the force needed to compress this spring 3 meters is 2100 N, what is the spring constant?

SOLUTION:

K U E

Find spring constant.

F = 2100 N kΔl = 3 m

k = 700 N/m

Stating the Problem

How far did the spring compress if all the energy from Batfink was transferred to the spring?

SOLUTION:

K U E

Find change in length.

Us = 9,800 J Δlk = 700 N/m

Δl = 5.29 m

I always conserve my Energy!