Starter quiz
- Match each symbol in the equations and with the quantity it represents.
- ⇔change in gravitational potential energy ✓
- ⇔mass ✓
- ⇔gravitational field strength ✓
- ⇔change in height ✓
- ⇔kinetic energy ✓
- ⇔speed ✓
- Match the following quantities to their units.
- energy⇔joules (J) ✓
- mass⇔kilograms (kg) ✓
- speed⇔metres per second (m/s) ✓
- gravitational field strength⇔newtons per kilogram (N/kg) ✓
- height⇔metres (m) ✓
- Which of the following statements are correct?
- Kinetic energy is directly proportional to an object's mass. ✓
- Kinetic energy is directly proportional to an object's speed.
- Gravitational potential energy is directly proportional to an object's mass. ✓
- Gravitational potential energy is directly proportional to an object’s speed.
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- An eagle with a mass 4.0 kg flies at a speed 15 m/s. Which of the following is the amount of energy in its kinetic store?
- 30 J
- 60 J
- 240 J
- 450 J ✓
- 900 J
-
- A book of mass 1.6 kg falls off a shelf onto the floor. The shelf is 2.0 m above the floor. Which of the following is the change in energy in the gravitational store? Use = 10 N/kg.
- 3.2 J
- 13.6 J
- 16 J
- 20 J
- 32 J ✓
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- An apple of mass 200 g falls from a branch that is 150 cm above the ground. Which of the following is the change in energy in the gravitational store? Use = 10 N/kg.
- 3 J ✓
- 30 J
- 300 J
- 3000 J
- 300 000 J
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Exit quiz
- The principle of ______ states that the total amount of energy at the end of a process is always the same as the total amount of energy at the beginning.
- 'conservation of energy' ✓
- A rock on a cliff has 1600 J of energy in the gravitational store. It falls onto the ground below and no energy is dissipated. Which of the following is the correct energy transfer during the fall?
- 1600 J is transferred from the kinetic to the gravitational store.
- 1600 J is transferred from the gravitational to the kinetic store. ✓
- Less than 1600 J is transferred from the gravitational to the kinetic store.
- More than 1600 J is transferred from the gravitational to the kinetic store.
- More than 1600 J is transferred from the kinetic to the gravitational store.
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- A 0.20 kg ball is thrown vertically upwards and reaches a maximum height of 2.1 m. Assuming that no energy is dissipated, the ball’s kinetic energy at the start is ______ J. Use = 10 N/kg.
- '4.2' ✓
- A plate is dropped. If no energy is dissipated during the fall, the final speed of the plate before it hits the ground is 4 m/s. If energy is dissipated, which of the following statements is correct?
- The final speed will be less than 4 m/s. ✓
- The final speed will still be 4 m/s.
- The final speed will be more than 4 m/s.
- It is impossible to say whether the final speed will be more or less than 4 m/s.
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- A child sledges down a hill of height 12 m. The total mass of child and sledge is 30 kg. Assuming no energy is dissipated, the kinetic energy at the bottom of the hill is ______ J. Use = 10 N/kg.
- '3600' ✓
- A mountain goat with a mass of 52 kg jumps vertically upwards, leaving the ground at speed 6.0 m/s. The maximum height that the goat can reach is ______ m. Use = 10 N/kg.
- '1.8' ✓
Worksheet
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Lesson Details
Key learning points
- Energy cannot be created or destroyed.
- In an ideal situation, no energy is dissipated.
- As an object changes height, change in gravitational potential energy = change in kinetic energy.
Common misconception
Energy can be lost or created in physical processes.
Always discuss how energy is dissipated to the surroundings when discussing energy transformations, even when dealing with ‘ideal situations’ in which there is no dissipation.
Keywords
Conservation of energy - The principle of conservation of energy states that the total amount of energy at the end of a process is always the same as the total amount of energy at the beginning.
Dissipate - Friction or air resistance can cause energy to dissipate into the surroundings as heat.
Gravitational potential energy - The energy an object has in its gravitational store is referred to as the object’s gravitational potential energy.
Kinetic energy - The energy an object has in its kinetic store is referred to as the object’s kinetic energy.
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