P3 | conservation of energy

Question 1

gravitational potential energy formula

Answer 1

GPE (J) = mass (kg) x gravity (N/kg) x height (m)

Question 2

kinetic energy formula

Answer 2

KE (J) = 1/2 x mass (kg) x velocity² (m/s)

Question 3

efficiency formula

Answer 3

(useful energy / total energy) x 100

Question 4

how does lubricating an object improve efficiency?

Answer 4

• a lubricant is a liquid which flows between objects
• this reduces friction
• this reduces the amount of energy transferred to the thermal energy store (which reduces wasted energy and increases efficiency)

Question 5

how do boiler jackets increase the efficiency of the boiler?

Answer 5

• jackets create a layer of air between the boiler and the surroundings
• this reduces energy wasted by conduction to the thermal energy store of the surroundings
• which improves the efficiency of the boiler