Work And Power Flashcards

1
Q

Name the unit for work, and it’s symbol

A

Joules J

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2
Q

Name the unit for power, and it’s symbol

A

Watts W

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3
Q

Calculate work done, given force and distance

A

W = Fd

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4
Q

Calculate force, given work done and distance

A

W = Fd
So F = W / d

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5
Q

Calculate power, given W and time

A

P = W / t

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6
Q

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.

A

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

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7
Q

Jessie is climbing a ladder. She has a mass of 51kg.
Calculate the work done to climb 2m above the ground.

A

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

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8
Q

It takes Jessie 10s to climb those 2m. Calculate the power exerted.

A

P = W/t
P = 1020 / 10 = 102W

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9
Q

If she had taken 5s instead of 10s, would the power exerted be more or less?

A

The power exerted would be higher. Since P = W / t, if t is decreased and W stays the same, P will increase.

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