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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