Energy Concepts

Front 1

Theidea that work is the product of a force and distance moved in the direction ofthe force when the force is constant

Back 1

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Front 2

Thecalculation of the work done for constant forces, when the force is not alongthe line of motion (work done = Fx cosθ)

Back 2

If force is applied to an object which moves, the work doneby the force on the object is calculated using W = FxCosθ, where F = Force, x =distance moved, θ = angle between the force and the direction of movement, soxCosθ is distance moved in the direction of force (θ is often 0, Cos0 = 1,so W =fx)

Front 3

Kineticenergy:

Back 3

Stationary object of mass m acted on by single constantforce, F, it accelerates in the direction of the force. When it has moved adistance x, its speed is v. W=fx (θ = 0), Acceleration a, given by F= ma, V^2 =u^2 +2ac, u = 0, v^2 = 2ax, ½ mv^2 = Fx, Fx=W=E

Front 4

GravitationalPotential Energy:

Back 4

Lift a body of mass m at constant velocity (without drag),Force F required to lift body is equivalent to mg. If a body is lifted ∆h thenWork done is given by W= F∆h = mg∆h

Front 5

ElasticPotential Energy:

Back 5

F is directly proportional to x, F = kx, k = spring constant,Area of triangle = ½bh, W = ½Fx, F = kx, W = ½ kx^2, W = ½F^2/kPrinciple of Conservation of Energy: Energy cannot be createdor destroyed only transferred

Front 6

Thework–energy relationship: Fx = ½mv^2 - ½mu^2

Back 6

Force (F) applied to body of mass (m) with speed (v) whichleads to Fx = ½ mv^2 – ½ mu^2, Work done = ∆KE

Front 7

Powerbeing the rate of energy transfer

Back 7

Work done per second

Front 8

Dissipativeforces, for example friction and drag, cause energy to be transferred from asystem and reduce the overall efficiency of the system

Back 8

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Front 9

Theequation: efficiency = (useful energy transfer / total energy input) × 100%

Back 9

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