A.3 Work, Energy and Power Flashcards

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1
Q

Mechanical energy

A

Energy possessed by an object due to it’s motion (kinetic) or position (potential)

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2
Q

Energy

A

Capacity to do work

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3
Q

In the absence of frictional or resistive forces, the total mechanical energy…

A

Is conserved

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4
Q

Work

A

When a force (F) moves an object through a displacement (s). (a transfer of energy)

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5
Q

What is the energy that an object loses or gains equal to?

A

The work done

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6
Q

If the force being used is not constant, the work done can be calculated by…

A

The average force value or the area below a force displacement graph

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7
Q

Centripetal force acts at 90* to…

A

The motion of the object undergoing circular motion

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8
Q

Does the centripetal force do any work in circular motion

A

No (no displacement in direction of the force)

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9
Q

Sankey diagram

A

Shows the flow of energy through a system and identify where the energy is lost to surrondings

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10
Q

Degraded energy

A

Energy that is lost from the system and cannot perform useful work

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11
Q

Power

A

The rate at which work is done or energy is transferred (W/Js-1)

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12
Q

Work formula

A

=force x displacement

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13
Q

When should you use W=Fscos0

A

If diplacement of the object is not along the line of action of the force

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14
Q

P=Fv

A

F is frictional force

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15
Q

Energy density

A

Energy liberated per unit volume of fuel consumed (Jm-3)

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16
Q

Work units

A

J

17
Q

What is the useful force in work done?

A

Fcos0

18
Q

If an object is being lifted, how much force is required?

A

Equal to object weight

19
Q

When can P=Fv be used?

A

When frictional force and velocity are constant

20
Q

Efficiency

A

Ratio of how much useful work or power we get out of a system

21
Q

Efficiency value/units

A

Value is between 0-1, no units and formula given in data booklet

22
Q

Why can a machine never be 100% efficient?

A

As some energy is always changed to thermal energy due to friction