Energy And Work Flashcards
Work done equation
Work done (joules) = force (newtons) X distance moved in the direction of the force (metres)
What is work done to overcome friction transferred as
Work done to overcome friction is transferred as energy that heats the objects that rub together and heats the surroundings
What is power
Power is the rate at which energy is transferred
What is the unit of power
The unit of power is the watt (w) which is equal to 1J/s
Power equation
Power (in watts) = energy transferred (J) / time taken (seconds)
When does the gravitational potential energy of an object increase
The gravitational potential energy of an I next increases when it moved up and decreases when the object moves down
Why does an object gain gravitational potential energy when it is lifted up
An object gains gravitational potential energy week it is lifted up because work is done on it to overcome the gravitational force
What is the change of gravitational potential energy of an object equal to
The change of gravitational potential energy of an object = it’s mass X the gravitational field strength X it’s change of height
What does the kinetic energy of an object depend on
The kinetic energy of a moving object depends on its mass and it’s speed
What is the kinetic energy of an object equal to
Kinetic energy (J) = 1/2 X mass (kg) X speed2 (squared) (m/s)2
Energy cannot be….
Energy cannot be created or destroyed
What does the conservation of energy apply to
Conservation of energy applies to all energy changes
Can energy be stored
Yes energy can be stored in various ways
What is useful energy
Useful energy is energy in the place we want it and in the form we want it
What is wasted energy
Wasted energy is the energy that is not useful energy
What happens to wasted energy eventually
Wasted energy is eventually transferred to the surroundings, which become warmer
What happens as energy dissipates
As energy spreads out (dissipates), it gets less and less useful
How to work out the efficiency of a device
Efficiency of a device = (useful energy transferred out of device / total energy supplied into device) X 100%
What is work done
Work is done on an object when a force makes the object move
Energy transferred = work done
