P1 conservation and dissipation of energy Flashcards
What is the conservation of energy?
Energy cannot be created or destroyed, only transferred between different stores
What energy transfers happen to a bungee jumper?
Gravitational potential to kinetic of human to elastic potential of rope to kinetic as it goes back up to gravitational potential and so on
Why does a bungee jumper not return to their original height?
Some energy is lost through thermal energy store of the surroundings
Relationship between work done and energy transferred
Work done = energy transferred
Work done equation
Work done = force x distance (W=Fs)
Units in work done equation
Work done = Joules (J)
Force = Newtons (N)
Distance = Metres (M)
When does an objects gravitational potential energy change
When an object is raised, it increases and when it is lowered, it decreases
Gravitational Potential Energy equation
Energy = mass x gravitational field strength x height (E = mgh)
Units in gravitational potential energy equation
Energy = Joules (J)
Mass = Kilograms (kg)
Gravitational field strength = Newtons per kilogram (N/kg)
Height = metres (m)
Kinetic Energy equation
Energy = 1/2 x mass x velocity^2 (E=1/2mv^2)
Units of kinetic energy equation
Energy = Joules (J)
Mass = Kilograms (kg)
Velocity = metres per second (m/s)
Hooke’s law
F = ke
Force = spring constant x extension
Elastic potential energy equation
Energy = 1/2 x spring constant x extension^2
(E = 1/2ke^2)
Units of elastic potential energy equation
Energy = Joules (J)
Spring constant = Newtons per metre (N/m)
Extension = Metres (m)
What is wasted energy
Energy not usefully transferred
What is useful energy
Energy that is usefully transferred
What is dissipation
When energy spreads out into the surroundings
Energy efficiency equation
Efficiency = useful output / total input (x100)
What is the maximum efficiency of an object
100%
What is relationship between power and energy transferred
Higher power = faster energy transfer
Power equation
Power = energy/ time
(P = E/ t)
Units of power equation
Power = Watts (W)
Energy = Joules (J)
Time = Seconds (s)
Power efficiency equation
Efficiency = useful power out / total power in
Weight equation
Weight = mass x gravitational field strength
(W = mg)
Units of weight equation
Weight = Newtons (N)
Mass = Kilograms (kg)
Gravity = Newtons per kilogram (N/kg)
What is gravity on earth
9.8
