Physics - Work, power and efficiency

Question 1

How is work done?

Answer 1

• A force is applied to an object which is moved
• This transfers energy

Question 2

What is a joule?

Answer 2

The energy transferred when a force of 1N causes a displacement of 1m

Question 3

What properties does a moving object have?

Answer 3

Mass and velocity

Question 4

What is the kinetic energy store of an object?

Answer 4

• Related to motion
• The faster an object moves, the more kinetic energy it has
• If a larger mass travels at the same speed, it has more kinetic energy

Question 5

What is the elastic potential energy store of an object?

Answer 5

• Relates to how stretched an object is
• The more stretched an object is, the more elastic potential energy it has

Question 6

What is the gravitational potential energy store of an object?

Answer 6

• Related to height above Earth
• The higher the object, the more GPE it has

Question 7

What is the gravitational field strength on the moon?

Answer 7

1.6 N/kg

Question 8

What is power?

Answer 8

The rate of transferring energy or the rate of doing work

Question 9

What is a watt?

Answer 9

A watt is equal to the transfer of one joule per second

Question 10

What does it mean if a kettle has a 3kW rating?

Answer 10

The kettle transfers 3000J of energy to the thermal store of the water per second

Question 11

What is the law for conservation of energy?

Answer 11

Energy cannot be created or destroyed, only stored and transferred

Question 12

What is the total energy output of a device equal to?

Answer 12

The total energy input

Question 13

What does efficient mean?

Answer 13

If a device is efficient it transfers energy usefully

Question 14

What happens to energy in an inefficient device?

Answer 14

Energy is wasted or dissipated as it is transferred to less useful stores

Question 15

How is energy usually lost?

Answer 15

To the surroundings through heating