Work Done Flashcards

(9 cards)

1
Q

What is work done? (2)

A

-When work is done, energy is transferred.
- This causes a change in the energy store

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2
Q

Which 3 processes transfer energy?

A
  1. Heating
  2. Radiation (light and sound)
  3. An electrical current
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3
Q

Can forces do work?

A

Yes (mechanically)

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4
Q

Give an example of forces doing work

A
  • When a bag is lifted, work is done against gravity
  • When the bag is released, work is done by gravity
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5
Q

What other force does work and what against?

A

Friction does work against moving objects

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6
Q

State the equation for work done

A

Work done = force applied x distance moved in direction of force
W = F x s
(Joules) (Newtons) (metres)

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7
Q

A 15kg goat is moved from the ground floor to the first floor in a lift. The first floor is 2.5m above the ground floor.
What is the work done?
(Hint: you will need two equations to answer this question)

A

E W=mg
U ✔️
S W=15 × 9.8
A ✔️
C 147N

E W= F x s
U ✔️
S W= 147 x 2.5
A ✔️
C 367.5 J= 370J to 2 s.f.

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8
Q

Define 1 Joule

A

1 Joule of energy is transferred when a force of 1N acts on an object for a distance of 1m in the direction of the force.

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9
Q

A brick is lifted 2.5m onto a wooden platform.
a. If the mass of the brick is 0.5kg, determine the work done on the brick.
b. How much does the store in GPE increase by?

A

a. The force used to lift the brick must be equal to the weight of the brick. Therefore:
Weight = mg = 0.5 × 9.8
Now we can determine the work done:
Work done = Fs = 4.9 × 2.5
= 12.25J
b. The work done on the mass = gain in GPE. Therefore, the brick gains Joules of GPE.

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