P1 - Conservation and Dissipation of Energy Flashcards
What actually happens to energy?
It is never used up.
Transferred between different energy stores and different objects.
What are the energy stores?
Thermal, Kinetic, Gravitational Potential, Elastic Potential, Chemical, Magnetic, Electrostatic and Nuclear Energy Stores.
How is energy transferred?
Either mechanically - physically doing work.
Electrically - work done by moving charges.
Heating/Radiation - Through light or sound.
What is a system?
A single object - e.g air in a piston.
A group of objects - two colliding vehicles that you’re interested in.
What happens if a system changes?
Energy is transferred.
Transferred into or away from the system.
Between different objects in the system.
Different types of energy stores.
What are closed systems?
Neither matter or energy can enter or leave.
Net change in Total energy = 0.
How can energy be transferred through heat?
Energy is transferred to the substance/object being heated - by heating.
Then, into the substances/objects thermal energy store.
How is energy transferred through physical work?
Work done = energy transferred.
When can work be done?
When current flows or by a force moving an object.
What force and energy stores are being used when throwing a ball upwards?
- Force exerted by a person upwards on the ball.
- Energy Transfer = Chemical Energy Store (User’s arm) - kinetic energy store of the ball.
What energy transfer happens if a ball is falling from the sky?
- Gravitational Force causes energy to be transferred from the ball’s Gravitational Potential Energy to its Kinetic Energy Store.
What happens during friction between a car’s wheels and brakes?
- Energy transfer from the wheels’ kinetic energy stores to the thermal energy store of the surroundings.
What happens in a collision between a car and a stationary object?
- Normal contact force between the car and the object does work.
- Causes energy to be transferred from the car’s kinetic energy store to other energy stores.
- An example is the elastic potential and thermal energy stores of the object and the car body.
- Some energy might also be transferred away by sound waves.
Movment in kinetic energy stores
- Anything that is moving has energy.
- Energy is transferred to this store when an object speeds up and is transferred away from this tore when an object slows down.
What does the energy in a kinetic energy store depend on?
- Objects mass and speed.
- The greater the mass, the faster it’s going
- The more energy there will then be in the kinetic energy store.
Equation for amount of Kinetic Energy
E(k)= 0.5 x m (kg) x v (m/s2)
Where do raised objects store their energy?
- Gravitational Potential Energy stores
- Lifting an object in a gravitational field requires work.
- Causes a transfer of energy to the gravitational potential energy store.
- The more the object is lifted, the more energy is transferred to the GP store.
What does the amount of GPE depend on?
Mass, Height and Strength.
Equation for Gravitational Potential Energy
GPE = E(p) = M (kg) x g (9.81N/kg) x height (m)
How do falling objects transfer energy?
From Gravitational potential energy stores to the kinetic energy store.
Equation for falling object w/ no air resistance
Energy lost from GPE store = Energy gained in Kinetic energy store.
What does affect does air resistance have on energy transfer?
Causes some energy to be transferred to other energy stores.
What energy will be transferred when stretching or squashing an object?
Elastic Potential Energy Store
Equation for Elastic Potential Energy
E (e)(Joules) = 0.5 x k (N/m) x e2 (m)
K = Spring Constant
e = extension of spring
