P1 Energy (page 167) Flashcards
Is energy used up?
It is never used up. It just transfers between different energy stores.
When energy is transferred to an object, what happens to the energy?
The energy is stored in one of the objects energy stores.
What are the energy stores? (you will need to know them)
Thermal Energy Stores
Kinetic energy stores
Gravitational Potential energy stores
Elastic Potential energy stores
Chemical energy stores
Magnetic energy stores
Electrostatic energy stores
Nuclear Energy Stores
Explain how Energy is transferred?
Mechancially (by a force doing work)
electrically (work done by moving charges)
heating
or by radiation e.g. light - page 220, or sound).
When a system changes, what happens to the energy?
The energy is transferred. It can be transferred into or away from the system between different objects in a system or between different types of energy stores.
What is meant by a system?
Its just a fancy word for a single object (e.g. the air in a piston), or a group of objects (e.g. two coliding vehicles) that you’re interested in.
What are closed systems?
They are systems where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.
Energy can be transferred by Heating. How is boiling water in a kettle energy transferred?
The boiling water in a kettle - think of this water as the system. Energy is transferred to the water (from the kettles heating element), by heating, into the waters thermal energy store (causing the temperature of the water to rise).
You could also think of the kettle’s heating element and the water together as a two-object system. Energy is transferred electrically to the thermal energy store of the kettles heating element, which transfers energy by heating to the waters thermal energy store.
Explain what is meant by ‘Word Done’?
its another way of saying energy transferred - they’re the same thing.
How can work be done (energy transferred)?
When current flows (work is done against resistance in a circut (see page 179), or by a force moving an object (more on page 203).
The initial force exerted by a person to throw a ball upwards does work, why?
It causes an energy transfer from the chemical energy store of the persons arm to the kinetic energy store of the ball and arm.
A Ball dropped from a height is accelerated by gravity. The gravitational force does work, why?
It causes energy to be transferred from the balls gravitational potential energy store to it’s kinetic energy store.
The friction between a cars breaks and its wheels does work as it slows down, why?
It causes an energy transfer from the wheels kinetic energy stores to the thermal energy store of the surroundings. (frictional forces cause a transfer of energy).
In a collision between a car and a stationary object, the normal contact force between the car and the object does work, why?
It causes energy to be transferred from the cars kinetic energy store to other energy stores. e.g. the elastic potential and the thermal energy stores of the object and the car body, some energy might also be transferred away by sound waves.
Describe the energy transfers that occur when the wind causes a windmill to spin? (2 marks)
Energy is transferred mechanically from the kinetic energy store of the wind (1 mark) to the kinectic energy store of the windmill (1 mark)
