Work and Energy:Work and Energy:

Jeopardy Review Game

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KineticEnergy

PotentialEnergy

Machines Work andPower

Bungee

Calculate the kinetic energy of a 3 kg toy cart that moves at

4m/s.

24 J

A hammer falls off a rooftop and strikes the ground with a certain KE.

If it fell from a roof that was four times higher, how would its KE of

impact compare? Its speed of impact?

KE would be 4X greaterSpeed would be 2X greater

Answer this question in terms of KE. Why does a small,

lightweight car generally have better fuel economy than a big,

heavy car?

Smaller mass means less kinetic energy for a given velocity.

A rollercoaster starts with a speed of 5.0 m/s at a point 45 m above the bottom of the dip. Neglect friction,

what will be the speed of the rollercoaster at the top of the next

slope, which is 30 m above the bottom of the dip?

18 m/s

1/2mv2 + mgh = 1/2mv2 + mghmasses cancel out – then you can solve for the velocity at the top of the second

hill.

What is the minimum speed of the ball at the bottom of its swing

(point B) in order for it to reach point A, which is 1.0 m above the

bottom of the pendulum?

4.5 m/s

What will be the kinetic energy of an arrow having a potential energy of

50J after it is shot from a bow?

50 J

What is the potential energy of a spring that has a spring constant

of 250 N/m when it is compressed 3.0 cm?

0.11 J

A 3.0 kg stone is dropped from a height of 10.0 m, and strikes the

ground with a velocity of 7.00 m/s. What average force of air

friction acts on it as it falls?

22.7 N

If a spring is compressed 0.25 m and when it is released it causes a 5.0

kg block to move 0.45 m/s on a frictionless surface, what is the k

value of this spring? What force was exerted on the block?

16 N/m4.1 N

In what two ways can a machine alter an input force?

By changing the magnitude or the direction.

What is the ideal mechanical advantage of this ramp?

5

What is the ideal mechanical

advantage of this pulley system? If it requires an effort

force of 1500 N to lift the 500 kg Load

what is the % efficiency of the

pulley?

IMA = 483% efficiency

What is the IMA of each of the level systems shown?

A = 1B = 2

C = 0.5

Work is required to lift a barbell. How many times more work is

required to lift the barbell three times as high?

Three times the work.

How much power is required to do 100 J of work on an object in a time of 0.5 s? How much power is required if the same work is done in 1 second?

200 W100 W

True or False:A machine decreases the amount of

work done on an object.

False! Less force over a greater distance.

Chris’s car can go from 0 to 100 km/h in 10 s. If the engine delivered twice the power to the wheels, how

many seconds would it take?

5 seconds

If a car traveling at 60 km/h will skid 20 m when its brakes lock,

how far will it skid if it is traveling at 120 km/h when its

brakes lock?

80 m

Describe how energy is transferred during a bungee jump.

Gravitational PE to Kinetic Energy to Spring Potential Energy then back to

KE and gravitational PE