Work, gravitational potential energy, and kinetic energy
Work done (J) = force (N) x distance moved (m)
Gravitational Potential Energy (J) = mass (Kg) x gravity (9.81 N/Kg) x height(m) (m)
To rearrange for mass =
𝐺𝑃𝐸
𝑔𝑟𝑎𝑣𝑖𝑡𝑦 𝑥 ℎ𝑒𝑖𝑔ℎ𝑡
for height =
𝐺𝑃𝐸
𝑚𝑎𝑠𝑠 𝑥 𝑔𝑟𝑎𝑣𝑖𝑡𝑦
Kinetic energy (J) = ½ x mass (kg) x [velocity]2 (m/s)
To rearrange for mass:
for velocity:
Work
1. Robert pushes a car for 60 metres with a force of 1000N. How much work has he done?
2. Gabrielle pulls a toy car 15 metres with a force of 200N. How much work has she done?
3. Jack drags a shopping bag for 1029 metres with a force of 150N. How much work?
4. Chloe does 2610J of work hauling a wheelbarrow for 6 metres. How much force is used?
5. A ball does 1500J of work being pushed with a force of 75N. How far does it travel?
Gravitational potential energy (GPE)
6. A 6kg cat is lifted 2.5m into the air. How much GPE does it gain?
7. A larger cat of 8kg is lifted 5m in to the air. How much GPE does it gain?
8. A massively fat cat of mass 18kg is lifted 7m into the air. How much GPE does it gain?
9. A large block of stone is held at a height of 19m having gained 4520J of GPE. How much
does it weigh?
10. A larger block of stone has been raised to a height of 17m has gained 6020J of GPE.
What mass does it have?
11. A really big beast of a block of stone of weight 800kg gains 36050J of GPE. How high has
it been raised?
12. A similarly huge block of stone has a mass of 660kg and gains 70080J of GPE. How high
has it been raised?
Kinetic energy
13. A raging bull of mass 750kg runs at 15 m/s. How much kinetic energy does it have?
14. A waddling armadillo of mass 50kg moves at 5 m/s. How much kinetic energy does it
have?
15. A stroppy teenager throws their PS4 controller at the wall after losing. It has 90.125J
of kinetic energy and moves at 23 m/s before it hits the wall. How much mass does it have?
16. A slightly disturbed man of 90kg runs directly into a wall with a kinetic energy of 4200J.
How fast is he running?
Combined questions
17. A rather unbalanced goat jumps off a cliff. The goat has a mass of 55kg and the cliff is
470m high. At what speed will the goat be travelling just before it hits the ground?
a. Work out the GPE
b. How much KE? (GPE lost = KE gained)
c. Rearrange the KE formula to work out velocity
18. Sam leaps out of an aeroplane to see if he can fly but quickly finds he cannot. He has
mass 96kg and the plane is cruising at 30,200m. Ignoring air resistance, at what speed will he
be travelling before he lands on a large pile of pillows, avoiding his certain death?
a. Work out the GPE
b. How much KE?
c. Rearrange the KE formula to work out velocity
19. David has a mass of 96kg. He slides down a slide, which goes 17m down. Calculate the
maximum speed he could reach at the bottom of the slide
a. Work out the GPE
b. How much KE? (GPE lost = KE gained)
c. Rearrange the KE formula to work out velocity
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