Chapter 16- Work, Energy, Power

Question 1

Define the unit of work

Answer 1

The joule is the amount of work done when a force of 1N is applied through a distance of 1m in the direction of the force (when a force moves an object through a distance)

Question 2

Give an example where kinetic energy is transferred to heat

Answer 2

Rubbing your hands together

Question 3

Give an example where heat energy can be transferred to kinetic energy

Answer 3

Heating water to create steam, which turns a turbine

Question 4

Define the unit of power

Answer 4

The rate of doing work (or the rate of converting energy)

Question 5

What is the equation for work

Answer 5

Work done (or energy transferred) (Joules) = force (N) x distance (m)

Question 6

What is the equation for kinetic energy?

Answer 6

Kinetic energy(j)= 1/2 x mass (kg) x speed squared

Question 7

What is the equation for gravitational potential energy?

Answer 7

Gravitational potential energy (j)= mass (kg) x gravitational field strength (N/kg) x height (m)

Question 8

What is the equation for power

Answer 8

Power (watts) = work done (j)/ time taken(s)

Question 9

Why is putting a fuse on an electrical device and earthing it a good idea?

Answer 9

• if there is a large current, it is important that this goes into the earth, instead of a person
• the fuse will break if there is a fault, transmitting the current elsewhere.
• this will break the circuit, preventing further damage
• this means the risk of shock is prevented

Question 10

What is the best location + climate for a solar power station?

Answer 10

LOCATON:
-low latitude - build on the equator
- enough area for solar panels (without shadow from hills + trees)
CLIMATE:
- sunny all year round
- not many rainy seasons/ dark seasons

Question 11

What is the best location + climate for a geothermal power station?

Answer 11

LOCATION:
- Accessible source of heat/ hot water in ground - a lot of volcanic activity
- not too close to cities/ populations
CLIMATE:
- doesn’t really matter, as geological power stations aren’t very affected by climate

Question 12

What are the negatives of wind power?

Answer 12

• unreliable: wind doesn’t always blow at the right speed
• could damage the view of an environment + can be noisy and can be a hazard to birds. The construction destroys habitats.
• a large, windy site is needed
• usually found in remote locations, so maintenance is difficult
• doesn’t produce a large amount of energy
• building a wind farm needs much money + time, and there is more money needed for maintenance, land and research

Question 13

What are the problems of waste from nuclear power stations?

Answer 13

• emits radiation, which is bad for the environment and people/ animals living in it
• needs long term storage and is expensive to contain and dispose of
• a lot of security and burial is needed
• needs to be stored away from a population