Energy Transfers Flashcards
What’s power
The rate at which energy is transferred
1 watt is an energy transfer of…
1 J per second
What’s the law of conservation of energy
Energy can be transferred usefully, stored or dissipated but it can’t created or destroyed
What’s a system
An object or a group of objects
In a closed system energy can’t…
Enter or leave
Friction causes energy to be transferred to…
Thermal energy
How to reduce unwanted energy transfers
Reducing friction
How to reduce friction
1) use a lubricant eg = oil at a fixed point
2) remove air particles around
At the start of a bungee jump all the energy is in…
The gpe store
As the bungee jumper falls energy’s transferred…
From the gpe store to the kinetic energy store
When the bungee rope starts to tighten….
The kinetic energy store is at its maximum
When the bungee rope is fully extended…
And all the energy’s been….
The kinetic energy’s at 0 - the jumper isn’t moving
Transferred to the epe store
When the bungee rope recoils the energy’s transferred…
To the epe store back to the kinetic energy store
During the ascent energy transfers…
From the kinetic energy store back to the gpe store
At the top of the ascent all the energy is in…
The gpe store
The bungee jumper never returns back to the original position because…
Energy is dissipated as thermal energy
because of friction with air particles
and stretching effects the bungee rope which isn’t fully elastic
When a force is used to move an object energy is…
Transferred - work
Work done equation
Work done = force x distance
W = F x s
J N m - units
When a car brakes what happens
The force if friction acts between the brake and the wheel
Kinetic energy store of the car is transferred to the thermal energy store of the brakes
The force of gravity acting on a person is…
Their weight
Energy equation
Energy = power x time
E =P x t
J W s - units
Charge equation
Charge = current x time
Q = I x t
C A s - units
Energy transferred equation
Energy transferred = charge flow x potential difference
E =Q x V
J C V - units
