Work Done Flashcards
(9 cards)
What is work done? (2)
-When work is done, energy is transferred.
- This causes a change in the energy store
Which 3 processes transfer energy?
- Heating
- Radiation (light and sound)
- An electrical current
Can forces do work?
Yes (mechanically)
Give an example of forces doing work
- When a bag is lifted, work is done against gravity
- When the bag is released, work is done by gravity
What other force does work and what against?
Friction does work against moving objects
State the equation for work done
Work done = force applied x distance moved in direction of force
W = F x s
(Joules) (Newtons) (metres)
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)
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.
Define 1 Joule
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.
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. 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.