Energy dissipation and conservation

Question 1

How can efficiency be increased?

Answer 1

The use of certain machines

Question 2

What are the two equations for efficiency?

Answer 2

Efficiency = useful output energy transfer / total input energy transfer

Efficiency = useful power output / total power input

Question 3

Define efficiency

Answer 3

The amount of energy that is usefully transferred

Question 4

Define dissipate

Answer 4

The energy either is scattered in all different directions or is used wastefully

Question 5

How is energy wasted?

Answer 5

It is dissipated into the surroundings as internal (thermal) energy

Question 6

State 3 ways ‘wasted’ energy can be avoided

Answer 6

Insulation, streamline design, lubrication of moving parts

Question 7

What is meant by the ‘ conservation of energy’

Answer 7

The amount of energy always stays the same so the energy cannot be created or destroyed, only changed from one store to another

Question 8

Unit for energy (KE, EPE, GPE,)

Answer 8

Joules (J)

Question 9

Unit for velocity

Answer 9

Metres per second (m/s)

Question 10

Unit for spring constant

Answer 10

Newton per second (N/s)

Question 11

Unit for extension

Answer 11

Mètres (m)

Question 12

Unit for mass

Answer 12

Kilogram (Kg)

Question 13

Unit for gravitational field strength

Answer 13

Newton per kilogram (N/Kg)

Question 14

Unit for height

Answer 14

Mètres (m)

Question 15

Equation for work done

Answer 15

Force x distance travelled

Question 16

What causes energy to be wasted / converted into thermal energy?

Answer 16

Frictional forces

Question 17

State ways of reducing thermal energy (wasted energy)

Answer 17

Reducing friction - using wheels, applying lubrication. Reducing air resistance, travelling slowly, streamlining.

Question 18

Equation for elastic potential energy

Answer 18

0.5 x spring constant x (extension) ²