Chapter 5 - Work, Energy and Power Flashcards

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1
Q

Define work done

A

Product of the magnitude of the force and the distance moved by the object in the direction of the force.

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2
Q

Define the joule.

A

Work done when a force of 1N moves an object 1m in the direction of the force.

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3
Q

Define energy

A

Capacity for doing work

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4
Q

Is energy scalar or vector?

A

Scalar

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5
Q

Define Kinetic Energy

A

Energy due to motion

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6
Q

Define Gravitational potential

A

Potential energy is equal (in magnitude, but negative) to the work done by the gravitational field moving a body to its given position in space from infinity.

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7
Q

Define Gravitational potential energy

A

Energy due to it’s height above the ground

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8
Q

Define Elastic potential

A

the energy stored as a result of a reversible change in an objects shape

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9
Q

Define Electric potential

A

energy of charges due to their position in a electric field

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10
Q

Define Sound energy

A

the energy of a mechanical wave due to the movement of atoms

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11
Q

Define internal energy

A

The sum of randomly distributed kinetic and potential energies of the molecules in a substance

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12
Q

Define electromagnetic energy

A

the energy from electromagnetic waves, stored within oscillating fields

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13
Q

Define nuclear energy

A

the energy stored in nuclei released when the nucleons rearrange

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14
Q

Define Chemical energy

A

the energy contained in chemical bonds, released when atoms rearrange

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15
Q

Principle of conservation of energy

A

in a closed system, energy cannot be created or destroyed, only transferred from one form to another.

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16
Q

Work done is equivalent to….

A

energy transfer

17
Q

Derive equation for KE

A
  • v^2 = u^2 + 2as
  • s = v^2/2a
  • if work done = force x distance (W = Fx)(x=s)
  • W = Fv^2/2a
  • F=ma, m=F/a
  • W = mv^2/2
    = 1/2mv^2
18
Q

Derive equation for GPE

A
  • GPE is an energy so W = Fx
  • under gravity, F = mg
  • GPE = mgx
  • GPE = mgh
19
Q

derive equation for impact speed under gravity

A
  • mgh = 1/2mv^2
  • 2gh = v^2
  • v = root(2gh)
20
Q

Define power

A

Rate of energy transfer P=E/t or rate at which work is done

21
Q

Define the watt

A

rate of energy transfer of 1 joule per second

22
Q

Equation to find power to move an object at constant velocity

A

P = Fv

23
Q

Equation for efficiency

A

(Useful energy out / Total energy in) x 100