Work and Energy Flashcards

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1
Q

If an object has energy then…

A

It has the ability to do work

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2
Q

What is the unit for energy?

A

The Joule ( J )

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3
Q

What is the work done a measure of?

A

The energy transferred

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4
Q

When does the work equal the total energy transferred?

A

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

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5
Q

What is GPE?

A

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

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6
Q

What is KE?

A

The energy an object has due to its motion.

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7
Q

What is Hooke’s Law?

A

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

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8
Q

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

A

The area below the graph?

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9
Q

Where must force be plotted?

A

The y axis

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10
Q

Where must extension be plotted?

A

The x axis

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11
Q

How does a streamlined car help?

A
  • 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
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12
Q

How does a lighter body and engine material help?

A

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

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13
Q

How does correctly inflated tires help?

A

Reduces rolling resistance and doesn’t heat up as much

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14
Q

How does a reduced engine idling loss help?

A

Saves fuel

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15
Q

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

A

The smaller the average force acting.

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16
Q

How are airbags a safety feature?

A

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.

16
Q

How are seatbelts a safety feature?

A

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.

16
Q

The greater the distance…

A

The smaller the average force acting during the collision.

16
Q

How are crumple zones a safety feature?

A

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.

16
Q

What does a longer time of collision mean?

A

A reduced decelerating force.