Work
Define Work
How energy is moved in and out of a system. A force over a given distance
What is a clue that an object may be storing energy as gravitational potential?
Height has changed from reference point of 0
What is the equation for gravitational potential
Ug = mgh
What is the law of conservation of energy. In words
Energy cannot be created or destroyed only transfered. Energy is the same initially as it is at the end, if a system is closed.
What is the formula for power. Give at least 3 variations of the formula
Power = Work/time
Power = (Force x Distance)/ t
Power = Change in Energy/ t
Power = Force x velocity
What is the formula for work
Work is force parallel times distance
What is a clue a system may be storing energy as kinetic?
It is moving
What is the equation for kinetic energy?
Ke = 1/2mv2
What is the law of conservation of energy in an equation
Initial Energy = Final Energy
E0 = Ef
What are the units of power?
Joules per second (J/s) or Watts (W)
What are the units for work
N*m or Joules
What is a clue a system may be storing energy as dissapated?
Friction heat, etc.
A roller coaster car traverses two vertical loops. Loop A is higher than Loop B. At the top of which loop will the car have a greater speed? Why?
Loop B. Since less energy is gravitational, more can be kinetic and velocity will therefore be greater.
A volleyball of mass 0.28 kg is dropped from the top of the bleachers (height equals 12 m). What is the speed of the volleyball right before it hits the gym floor?
15 m/s
Who does more work, person 1 (50 kg) walking up 20m stairs in 10 seconds or person 2 (50kg) walking up the same stairs in 3 seconds? Who has more power?
Same work, person 2 has more power.
150 J
What is a clue a system may be storing energy as elastic?
There is a spring, a bounce or a stretch
A box is lifted 2.2 m above its initial height (h = 0) and its GPE increases by 7.2 J. What is the mass of the box?
0.33 kg
A 4 kg object is dropped off a 50 meter high building. At 5 meters above the ground, what is the velocity of the object?
30 m/s
A runner goes up the stairs using 200 J of work in 10 seconds. What is their power?
20 watts
How much work is done if I push a 100 N crate across a frictionless floor with a force of 500N from a distance of 10 meters?
a) by me
b) by gravity
c) by the normal force
a) 500 J
b) 0
c) 0
What are the units of energy? Give two answers.
Joules or Newtons times meters
If velocity is halved, what happens to kinetic energy?
It is 1/4 of what it was before
In our roller coaster lab, we found that energy was not conserved when we released a car on a u - shaped track. Why?
There was friction - some energy was Edis and so energy was not conserved.
400 Watts