AS1 1.8 Work Done, Potential Energy and KE Flashcards
Define “work done”
The product of the force and the distance moved in the direction of the force
Define “power”
The rate of doing work
Define “efficiency”
The fraction of input energy that does work
Define “kinetic energy”
The product of half the mass and the velocity squared
define “(Gravitational) potential energy”
The product of mass, gravitational field strength and height
What happens to energy when work is done?
Energy is transferred from one form to another
What is the equation for work done?
(Work done = force x distance)
(W = Fs)
What is the principle of conversion of energy?
Energy cannot be created or destroyed, only transferred from one form to another.
What is the equation for power?
(Power = Work done / Time)
(P =W/T)
what is the equation for efficiency?
(eff = useful energy out / total energy in)
What is the equation for kinetic energy?
(Kinetic Energy = 1/2 Mass x (velocity^2))
(KE = 1/2mv^2)
What is the equation for gravitational potential energy?
(Gravitational potential energy = mass x velocity x height)
(Ep - mgh)
What is the principle of conservation of energy in terms of kinetic and gravitational energy if we ignore resistive forces?
loss of Ek(KE) = gain in Ep(GPE)
loss of Ep(GPE) = gain in Ek(KE)
What are resistive forces with examples?
Resistive forces are forces that act on a moving body in the opposite direction to the direction of movement.
examples - friction
What is the principle of conservation of energy?
energy is never created or destroyed, just transferred from one energy to another
What is the calculation for the exchange between gravitational potential energy and kinetic energy?
initial KE + initial GPE = final KE + final GPE + work done against friction
what is the equation for the loss in kinetic energy?
1/2mv^2 - 1/2 u^2 = Fs
what is another equation for power (velocity)?
Power = force x velocity
(P = Fv)
what is energy conservation and energy efficiency ?
energy conservation - the act of saving energy by reducing the use of a service
(E.G: unplugging appliances when not in use)
energy efficiency - saving energy but keeping the same level of service
(E.G: washing clothes using cold water)
what are the 3 reasons for energy efficiency and conservation?
- Environmental
- Financial
- Social
what is the environmental impact from energy conservation and efficiency?
- CO2 emissions
- Global warming
- Climate change
what is the financial impact of energy efficiency and conservation?
- reduced running costs (more disposable income)
- boosts economy
- reduced taxation
- local labour used for installs (employment and economic growth)
what is the social impact of energy efficiency and conservation
- better quality of life
- improved self being
- increased energy security (fossil fuels are finite)
