Efficiency (in terms of useful energy transferred) | Physics

Starter quiz

Which of the following forces slow down a sledge that is sliding down a snow-covered hill?
- air resistance ✓
- friction ✓
- gravitational
- normal reaction force
Which of the energy stores does friction transfer energy into?
- chemical store
- gravitational store
- kinetic store
- thermal store ✓
Match the energy stores on the left to their descriptions on the right.
- chemical store
  
  ⇔
  
  energy due to chemical reactions ✓
- gravitational store
  
  ⇔
  
  energy due to an object's mass and height ✓
- kinetic store
  
  ⇔
  
  energy due to an object's mass and speed ✓
- thermal store
  
  ⇔
  
  energy due to particle movement ✓
Why does a hot cup of tea cool down?
- All of its energy is used up.
- All of its energy is transferred to the surroundings.
- Some of its energy is used up.
- Some of its energy is transferred to the surroundings. ✓
Why is the rebound height of a ball not the same as the height that it was dropped from?
- Earth's gravitational force is pulling the ball downwards.
- The normal reaction force from the ground is less than the gravitational force.
- Pushing air out of the way uses up some of the ball's energy.
- Pushing air out of the way transfers some energy to the air particles. ✓
The law of conservation or energy states that energy cannot be created or ...
- 'destroyed' ✓