P1 Knowledge Organiser Part A (1) Flashcards
What is a system?
A system is an object or group of objects.
What is a closed system?
A closed system is one where no energy can escape to or enter from the surroundings. The total energy in a closed system never changes.
What is work done?
Work done is when a force moves or changes the shape of an object, transferring energy to the object.
What is the unit for energy?
The unit for energy is joules (J).
What is one joule of work?
One joule of work is the work done when a force of 1 N causes an object to move 1 m in the direction of the force.
Describe the energy transfer when a moving car slows down.
Energy is transferred mechanically from the kinetic store of the car to the thermal store of its brakes. Some energy is dissipated to the thermal store of the surroundings.
Describe the energy transfer when an electric kettle is used to heat water.
The electric current in a kettle transfers energy to the heating element’s thermal store. Energy is then transferred by heating from the heating element’s thermal store to the thermal store of the water.
Describe the energy transfer when a falling apple hits the ground.
Energy is transferred from the kinetic store of the apple and dissipated to the thermal store of the surroundings by sound waves.
Name the unit that represents one joule transferred per second.
The unit that represents one joule transferred per second is the watt (W).
A motor is 30% efficient. What does that mean?
It means that 30% of the energy is usefully transferred and 70% is dissipated.
Describe the energy transfer when a battery-powered toy car is used.
Energy is transferred electrically from the chemical store of the battery to the kinetic store of the toy car. Some energy is dissipated to the thermal store of the surroundings.
Describe the energy transfer when a ball is fired using an elastic band.
Energy is transferred mechanically from the elastic store of the elastic band to the kinetic store of the band. Some energy is dissipated to the thermal store of the surroundings.
Name the five energy stores.
The five energy stores are kinetic, gravitational potential, elastic potential, thermal, and chemical.
Name the four ways in which energy can be transferred.
Energy can be transferred by heating, waves, electric current, and mechanically (by forces).
What is efficiency?
Efficiency is a measure of how much energy is transferred usefully.
How do you calculate efficiency as a decimal?
Efficiency = useful output energy transfer (J) / total input energy transfer (J).
How do you express efficiency as a percentage?
To express efficiency as a percentage, multiply the decimal result by 100 and add the % sign.
What happens to energy in a system?
Energy cannot be created or destroyed; it can only be transferred usefully, stored, or dissipated (wasted).
