Work and Energy

Question 1

If an object has energy then…

Answer 1

It has the ability to do work

Question 2

What is the unit for energy?

Answer 2

The Joule ( J )

Question 3

What is the work done a measure of?

Answer 3

The energy transferred

Question 4

When does the work equal the total energy transferred?

Answer 4

If no energy is lost as heat to the surroundings (by air resistance or friction)

Question 5

What is GPE?

Answer 5

The energy an object has due to its height above the ground.

Question 6

What is KE?

Answer 6

The energy an object has due to its motion.

Question 7

What is Hooke’s Law?

Answer 7

For a material or a spring the extension is directly proportional to the force provided the limit of proportionality is not exceeded.

Question 8

What shows the work done to stretch or compress the string?

Answer 8

The area below the graph?

Question 9

Where must force be plotted?

Answer 9

The y axis

Question 10

Where must extension be plotted?

Answer 10

The x axis

Question 11

How does a streamlined car help?

Answer 11

• It reduces drag
• Reduces air resistance and allows for greater speed.
• Less work needs to be done by the engine, allowing for better fuel economy

Question 12

How does a lighter body and engine material help?

Answer 12

Reduces inertia
Acceleration rates are greater and less fuel will be used.

Question 13

How does correctly inflated tires help?

Answer 13

Reduces rolling resistance and doesn’t heat up as much

Question 14

How does a reduced engine idling loss help?

Answer 14

Saves fuel

Question 15

A lot of KE is transferred into EPE and the greater the distance/shape change…

Answer 15

The smaller the average force acting.

Question 16

How are airbags a safety feature?

Answer 16

It is designed to deflate as the person hits it with their head. The KE of the head is transferred to other forms of energy with a reduced decelerating force.

Question 16

How are seatbelts a safety feature?

Answer 16

Prevents the occupants being ‘thrown forward’. It is also designed to stretch so the person being restrained decelerates over a longer distance and period of time.

Question 16

The greater the distance…

Answer 16

The smaller the average force acting during the collision.

Question 16

How are crumple zones a safety feature?

Answer 16

Certain parts of the car are designed to easily change shape during a collision. In effect, these zones absorb a lot of the car’s KE and changes it to EPE, reducing the average force during the collision.

Question 16

What does a longer time of collision mean?

Answer 16

A reduced decelerating force.