Work And Power Flashcards
Name the unit for work, and it’s symbol
Joules J
Name the unit for power, and it’s symbol
Watts W
Calculate work done, given force and distance
W = Fd
Calculate force, given work done and distance
W = Fd
So F = W / d
Calculate power, given W and time
P = W / t
Beth is pushing a trolley up a ramp. The trolley has a weight of 280N. The height of the ramp is 1.8m. Calculate the work done to get the trolley to the top of the ramp.
W = Fd
Work is being done against gravity, so the force needed is equal to the trolleys weight force (F = 280N) and the distance is equal to the upwards distance (d = 1.8m)
W = 280 x 1.8 = 504J
Jessie is climbing a ladder. She has a mass of 51kg.
Calculate the work done to climb 2m above the ground.
W = Fd
The force needed is equal to Jessie’s weight force as work is being done against gravity to allow her to climb.
Fw = mg
Fw = 51 x 10 = 510N
W = 510 x 2 = 1020 J
It takes Jessie 10s to climb those 2m. Calculate the power exerted.
P = W/t
P = 1020 / 10 = 102W
If she had taken 5s instead of 10s, would the power exerted be more or less?
The power exerted would be higher. Since P = W / t, if t is decreased and W stays the same, P will increase.