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AS Level CIE physics > Work, Energy, Power > Flashcards

Work, Energy, Power Flashcards

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1
Q

State what is meant by work?

A

If a force displaces a point (object) along direction of force we say that the force has done work.

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2
Q

Define work done?

A

Work=Force x Distance travelled along force.
Where:
Work=Nm (Joule)
Force=N
Distance=m

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3
Q

Define what is meant by 1 joule?

A

If a force of one newton displaces a point by 1 meter along the direction of force a work of one joule is done on the point.

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4
Q

How can we calculate the work done by applied force?

A

Work done by applied force: Applied force x distance travelled along force.

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5
Q

How do we calculate work done by net force?

A

Work done by net force acting: Net force x distance.
(F-Fr) s
ma s

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6
Q

How do we calculate work done against resistive forces?

A

Total resistive forces x distance.
Fr x s
(this is also known as work done dissipated as heat).

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7
Q

What energy is work done equivalent to?

A

Work done=Change in Kinetic energy

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8
Q

Explain how work done by net force is equivalent to kinetic energy?

A

Work done by net force=(F-Fr) s
=ma s 2as=v^2-U^2 as=v^2-u^2/2
=m (v^2-u^2/2)
=1/2 m (v^2-u^2)
=1/2 mv^2-1/2mu^2
=change in kinetic energy

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9
Q

How do we calculate work done if force acts an angle?

A

Work done= Component of force x distance travelled.
W=Fcosθ x S
W=FScosθ

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10
Q

What are the different types of energy?

A

Electrical energy
Chemical energy
Thermal energy
Atomic Energy
Mechanical energy

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11
Q

What are the two types of mechanical energy?

A

Potential energy
Kinetic Energy

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12
Q

State what is meant by kinetic energy?

A

Kinetic energy is the energy of a mass due to its motion.

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13
Q

What are the two types of potential energy?

A

Gravitational potential energy.
Elastic potential energy.

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14
Q

State what is meant by elastic potential energy?

A

Elastic potential energy is the energy stored in an object due to extension/compression/change of shape.

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15
Q

State what is meant by gravitational potential energy.

A

Gravitational potential energy is the energy stored in a mass due to its position in a gravitational field.

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16
Q

What is the formula for gravitational potential energy?

A

ΔEg=mgΔH
where Eg=Gravitational Potential energy
m=mass
g=gravitational field strength
ΔH=Change in height

17
Q

What is the formula for Elastic potential energy (strain energy)?

A

Ee=1/2 Fx
But F=kx
Ee= 1/2 kx^2
If x changes from x1 to x2
ΔE=1/2 k (x2^2-x1^2)

18
Q

What is the formula for kinetic energy?

A

1/2 mv^2

19
Q

What is energy?

A

Ability to do work is called energy.

If it is done then it is work.
If it can be done it is energy.

20
Q

What are the two types of energy?

A

Renewable sources and Non Renewable sources of energy.

21
Q

What are renewable sources of energy?

A

Sources that are available in abundance and will not run out in the near future.

22
Q

Give examples of renewable sources of energy.

A

Solar energy (Wind/Hydroelectric)
Nuclear energy
Geothermal energy
Tidal energy.

23
Q

What are non-renewable sources of energy?

A

Energy sources that are scarce and will eventually run out, in the foreseeable future.

24
Q

Give an example of non-renewable

A

Fossil fuel.

25
Q

What is change of energy equal to?

A

Change of energy=Work done by the system.

26
Q

What is the law of conservation of energy?

A

Energy can neither be destroyed nor created, it is always conserved. We can only convert one form to the other.

27
Q

What is a transducer?

A

Any object or system that converts one form of energy to another is called a transducer.

28
Q

Give an example of a transducer.

A

A dry cell converts chemical energy to electrical energy or for a falling rock gravitational potential energy is converting into kinetic energy.

29
Q

How do we calculate efficiency?

A

Efficiency= Useful output/Total Input
Where input and output are measured in power or energy/ W or J

30
Q

What are the units of efficiency?

A

Efficiency has no units because it is a ratio between same quantities.

31
Q

How do we calculate percentage efficiency?

A

% efficiency=efficiency x 100.

Percentage efficiency= Useful Output/Total input x 100

32
Q

Define power.

A

Power=Work Done/Time taken.
P=W/t
Power=Watt
Work Done=Joule
Time taken=seconds

33
Q

What is one watt.

A

Watt is a unit of power, if a work of one joule is done, in one second a power of one watt is developed.

34
Q

How can we calculate work done when given energy?

A

Work done=Energy converted from one form to the other.

AS Level CIE physics (8 decks)

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