Energy and motion II Flashcards

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1
Q

What is work done?

A

When a force moves an object through a distance and energy is transferred (kinetic energy transferred = work done)

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2
Q

What is gravitational potential energy due to?

A

A change in height

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3
Q

What is kinetic energy?

A

The energy of movement

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4
Q

What happens when an object falls?

A

Its gravitational potential energy is converted into kinetic energy, some of which is then turned into heat and sound energy

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5
Q

What happens to work done when you stretch an object?

A

It is stored as elastic potential energy

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6
Q

What happens when the force stretching an object is removed?

A

The elastic potential energy is converted to kinetic energy and the object returns to normal

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7
Q

The extension of an elastic object has what relationship with the force?

A

Directly proportional

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8
Q

What is a spring constant?

A

A value that depends on the material you stretch, which is representative of how stiff the spring is

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9
Q

What happens when too much force is applied to a spring?

A

The spring reaches the limit of proportionality. After this, the spring extension and force aren’t proportional, and the material will be permanently stretched

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10
Q

What is power?

A

Power is the rate of doing work (how quickly you get something done)

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11
Q

What is one watt?

A

One joule of energy transferred per second

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12
Q

What is momentum?

A

A property of moving objects

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13
Q

How does an object have a greater momentum?

A

By having a greater mass and a greater velocity

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14
Q

What properties does momentum have?

A

Size and direction

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15
Q

What is the relationship between momentum before and after an event?

A

Momentum remains the same before and after an event

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16
Q

What changes momentum?

A

Forces that act on an object

17
Q

How do brakes work?

A

By working against the kinetic energy of the car, transferring it into heat & sound

18
Q

How do regenerative brakes work?

A

Regenerative brakes put the wheel’s motor into reverse so the wheels are slowed, and the motor turns kinetic energy into electrical energy that is stored as chemical energy in a battery to reuse

19
Q

What is safe conversion of kinetic energy and how does it help passengers in cars?

A

Increasing the time over which momentum changes happen which lessens the force on the passengers

20
Q

What are the main methods of conversion of kinetic energy?

A

Crumple zones- kinetic energy is converted as it changes shape, increasing impact time
Side impact bars- help direct kinetic energy away from passengers
Seatbelts- stretch slightly, increasing time taken for wearer to stop
Airbags- stop you hitting hard surfaces