3
How much work is done on a 20-N crate that you lift 2 m?
40J
How much power is expended if you lift a 60 N crate 10 meters in 1 second?
600 W
How many joules of work are done on a box when a force of 25 N pushes it 3 m?
75 J
How much power is required to do 40 J of work on an object in 5 seconds?
8W
If you life two loads up one story, how much work do you do compared to lifting just one load up one story?
Twice as much
If you lift one load up two stories, how much work do you do compared to lifting one load up one story?
Twice as much
Power is defined as..?
Work done on an object divided by the time taken to do the work
A ball is thrown into the air with 100 J of kinetic energy which is transformed to gravitational potential energy at the top of its trajectory. When it returns to it original level after encountering air resistance, its kinetic energy is...
less than 100 J
Kinetic Energy on an object is equal to..?
one half the product of its mass times its speed squared
an object at rest may have:velocity; kinetic energy; potential energy; momentum
potential energy
A job is done slowly, and an identical job done quickly. Both jobs require the same amount of work but no different amounts of..?
power
it takes 160 J to push a large box 2 m across a floor. Assuming the push is in the same direction as the move, what is the magnitude of the force on the box?
80 (f=w/d)
An arrow has 50 joules of PE. Assuming no loss of energy to heat, how much KE will it have after it has been shot? Why?
It will have 50 joules of PE. It stays the same
The unit for work is.. ?
Joules
If an object has kinetic energy, then it also must have
Momentum
An object that has kinetic energy must be at rest or moving?
Moving
Which has greater kinetic energy, a car traveling at 30 km/h or a half-as-massive car traveling at 60 km/h
The 60 km/h
As a pendulum swings back and forth describe what is happening in terms of kinetic and potential energy.
The total amount of energy is conserved. At the top of the swing, there is PE but no KE. At the bottom of the swing, there is KE but no PE.
Consider molecules of hydrogen gas and molecules of heavier oxygen gas that have the same kinetic energy. The molecules with the greater speed are
hydrogen
When a car's speed triples, its kinetic energy..?
increases 9 times because velocity is squared
Suppose a moving car has 3000 J of kinetic energy. If the car's speed doubles, how much kinetic energy will it then have?
12,000 J
a person on a roof throws one ball downward and an identical ball upward at the same speed. the ball thrown downward hits the ground with 140 J of kinetic energy. ignoring air friction, with how much kinetic energy does the second ball hit the ground?
140 J
Which requires more work: lifting a 50-kg sack a vertical distance of 2 m or lifting a 25-kg sack a vertical distance of 4 m?
Both take the same 1000 J.
An object at rest may have
energy
in physics the equation for work is
force x distance (W = F * d)
A small economy car (low mass) and a limousine (high mass) are pushed from rest across a parking lot, equal distances with equal forces. The car that receives more kinetic energy is the
limousine
Potential energy is the energy an object has because of its..?
location
An object that has kinetic energy must have...
momentum
if kelly the skater's speed increases so he has three times the momentum, then his kinetic energy increases by
nine times
