Mechanics 4 - Work, Energy and Power Flashcards

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1
Q

What is the principle of conservation of energy?

A

Energy cannot be created or destroyed, only transferred from one type to another.

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2
Q

How does an object gain energy from a force?

A

When the force does work on the object (same direction as movement)

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3
Q

How does an object lose energy?

A

By doing work against a force (usually frictional)

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4
Q

What’s wrong here?

A

In W=Fs you multiply the parallel components

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5
Q

When using W=Fs what must be the case?

A

The components must be parallel

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6
Q

What is the work done by the weight of this block?

A

0 because the weight is perpendicular to the movement

So there is no parallel component to displacement

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7
Q

If two objects are dropped from the same height and air resistance is negligible, which hits the ground first?

A

Both hit at the same time because they both accelerate at 9.81ms-2

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8
Q

How do you calculate the velocity the object hits the ground using GPE and KE (assuming no air resistance)

A

Energy equivalency (only works when air resistance = 0)

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9
Q

What is power?

A

The rate of transfer of energy

or

The rate at which work is done

(Measured in Watts [W])

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10
Q

What is wrong here?

A

For P=Fv, F is not the resultant force

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11
Q

How do you calculate efficiency?

A
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12
Q

If the system is not 100% efficient would this be correct?

A

No, because some GPE is converted to thermal and kinetic energy of the snow (working against friction)

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