Topic 1a - Energy Transfers Flashcards
Where is energy stored?
When energy is transferred to an object, the energy is stored in one of the object’s energy stores.
What are 8 energy stores?
- Kinetic
- Thermal
- Chemical
- Gravitational Potential
- Elastic Potential
- Electrostatic
- Magnetic
- Nuclear
What is a system?
A system is an object or group of objects.
What is a closed system?
A system where neither matter nor energy can enter or leave. The net change in the total energy of a closed system is always zero.
What happens when a system changes?
Energy is transferred. It can be transferred, into or away from a system, between different objects in the system, or between different energy stores.
What are the 3 main types of energy and what do they mean?
- Kinetic energy - energy of an object that is in motion.
- Potential energy - energy that has the potential to be converted into another form of energy. Eg, gravitational potential energy or elastic potential energy.
- Heat/Thermal energy - something that gives out heat or becomes hot, normally due to the presence of a frictional force.
What are 6 other examples of energy, that aren’t the main 3?
- Solar energy
- Nuclear energy
- Hydroelectric energy
- Chemical energy
- Tidal energy
- Wave energy
What is the law/principal of conservation of energy? (2)
- In a closed system, the total energy before a process is the same as the total energy after the process.
- Energy can never be created or destroyed, it can only be converted from one form to another, and stored/dissipated.
How does energy change when an object is projected upwards? (3)
- Before the ball is thrown upwards, the person holding the ball has energy in their chemical store.
- When the ball is thrown, some of that energy is transferred to the kinetic store of the ball as it begins to move upwards.
- As the height of the ball increases, energy from the kinetic store of the ball is transferred to its gravitational potential store.
How does energy change when a moving object hits an obstacle? (3)
- When an object, such as a car, is moving, energy in the chemical store of the fuel is transferred to the kinetic store of the car.
- If the object hits an obstacle, such as the car hitting a wall, the speed of the car will decrease very quickly.
- Therefore, the energy in its kinetic store will decrease.
Where does the energy transfer to when a moving object hits an obstacle? (3)
- In the scenario of a car hitting a wall, most of the energy from its kinetic store is transferred to the thermal store of the surroundings (dissipated).
- Energy is transferred mechanically to the thermal store of the wall (the force of the car on the wall).
- Energy is also transferred by heating to the thermal store of the car, the wall. and to the thermal store of the air as the sound waves transfer energy away from the system (causing the air particles to vibrate).
How does energy change when a vehicle is accelerated by a constant force? (2)
- When a vehicle is stationary, it has energy in the chemical store of the fuel.
- When the vehicle speeds up or accelerates, the energy is transferred to the kinetic store of the car.
How does energy change when a vehicle slows down? (4)
- When a vehicle is moving, it has energy in its kinetic store.
- As it slows down or decelerates, energy is transferred to the thermal store of the surroundings (dissipated).
- This energy is transferred by heating due to friction between the tyres on the ground, and due to friction between the brakes and the brake pads.
- Energy is also transferred by heating as the sound waves transfer energy away from the system (making the air particles vibrate).
How does energy change when water boils in a kettle? (2)
- When an electric kettle boils water, energy is transferred by electrical working from the mains to the thermal store of the heating element inside the kettle.
- As the heating element gets hotter, energy is transferred by heating to the thermal store of the water.
What is the transfer pathway of mechanical working?
When a force acts on an object (e.g. pulling, pushing, stretching, squashing).
What is the transfer pathway of electrical working?
A charge moving through a potential difference (e.g. current).
What is the transfer pathway of heating by particles?
Energy is transferred from a hotter object to a colder one (e.g. conduction).
What is the transfer pathway of heating by radiation?
Energy transferred by electromagnetic waves (e.g. visible light).
What do all objects in motion have?
Kinetic energy
What is the equation for kinetic energy?
- KE = 1/2 m v(2)
- KE - energy in joules, J
v - speed in m/s
m - mass in Kg
What does gravitational potential energy depend on?
How far up/down an object is relative to the ground or another surface. The further up an object is, the larger its gravitational potential energy.
What is the equation for gravitational potential energy?
- GPE = mgh
- m - mass in Kg
g - gravitational field strength in N/kg
h - height in metres, m
GPE - in joules, J
What is the gain in GPE equal to?
The work done in lifting.
What happens when objects are released from a height/when they lose height?
The GPE is converted into KE, provided there is no work done against friction.