Work and Energy Flashcards
Equations for power
P = W/t = Fv
Elastic potential energy equation
PE (elastic) = 1/2 kx^2
Net work equation
Work (net) = Fdcosθ = ∆KE = W(C) + W(NC)
W(nc) = ∆KE + ∆PE
Conservation of Mechanical Energy
∆KE + ∆PE = 0
KE1 + PE1 = KE2 + PE2
At the maximum height, what is PE and KE?
KE is 0 and PE is max
Changing the length of a ramp from 2m to 3m, how much would potential energy change?
PE would not change because there is no change in height
How much more work would it take to stop a car if the friction force was reduced due to a rainy day? Assume same initial velocity
Same work
Friction force is reduced but the displacement will also increase. Work is the same because change in KE is the same for both conditions because it only depends on initial and final speed. Both final speeds are 0.
Work by change in potential energy
W = -∆PE
The weight of an object is…
The normal force
Escape velocity is….
The speed needed to escape a planet’s gravitational pull, when gravitational potential energy + kinetic energy is 0
U = - (GMm)/r
0 = - (GMm)/r + 1/2 mv^2 v = sqrt[ (2GM)/r ]
What does increasing the height released of an object do to its final speed?
Increases the speed it reaches
If a roller-coaster is released at a height of h1, what is the maximum height it can reach assuming no friction and no extra energy is supplied?
The maximum height would be h1
If the height an object is released from rest is doubled, then what would happen to the velocity at the bottom of the path?
Velocity increases by sqrt(2)
If the velocity to throw a ball upwards is doubled, what would happen to the maximum height?
Maximum height would increase by 4
If a ball is rolled down a rough hill, will all the potential energy at the beginning be converted to kinetic energy at the bottom?
No, FRICTION!!
The kinetic energy at the end will be less than the initial potential energy because some of the energy will be lost due to heat/friction
