Module Review

1.1.1 Systems and Energy Stores

System and Energy Stores

• A system is an object or a group of objects.
• Energy is what makes things happen or change.
• Energy stores are where objects keep energy.
• There are eight main types of energy stores: thermal, kinetic, gravitational potential, elastic potential, chemical, magnetic, electrostatic, nuclear.
• Thermal energy is the energy stored in an object from the movement of the particles that the object is made of.
• Kinetic energy is the energy stored in an object because it is moving.
• Gravitational potential energy is the energy stored in an object from the gravitational force pulling the object towards the Earth.
• Elastic potential energy is energy stored in an object when it is stretched out or compressed.
• Chemical energy is energy stored in an object’s chemical bonds.
• Magnetic energy is energy stored when two magnets, or a magnet and a magnetic material, are attracted or repelled.
• Electrostatic force is the energy stored when charged objects are attracted or repelled.
• Nuclear energy is the energy stored inside the nucleus of an atom and released during nuclear reactions.

Total Energy, Net Energy and Closed Systems

• The total energy of the system is the sum of all the energy in all the energy stores in the system.
• Net energy is the change in the total energy of a system.
• Net energy can be calculated as the energy transferred into the system, minus the energy transferred out of the system.
• The unit of energy is Joules (J).
• Closed systems are systems where no energy or objects can enter or leave the system.
• The total energy of a closed system is always the same.
• The net energy of a closed system is always zero as no energy can enter or leave the system.

System Changes and Energy Transfers

• When a system changes, energy is always transferred.
• The movement of energy from one energy storeThe stage where the CPU saves the result of the execution back into memory or registers. to another is called an energy transfer.
• Energy can be transferred in two ways, by doing work or by heating.
• Work done means energy transferred.
• There are two ways work can be done, by a force moving an object or by an electrical current flowing. 
• Heating is the energy transfer from one object’s thermal energy stores to another object’s thermal energy stores.

Energy Changes in Common Situations

• When a person throws a ball up, the force exerted by the person on the ball does work. Energy is transferred from the person’s chemical energy stores to the ball’s kinetic energy stores.
• When a ball falls down, the gravitational force does work on the ball. Energy is transferred from the ball’s gravitational potential energy stores to its kinetic energy stores.
• When an electric kettle brings water to a boil, heating takes place. Energy is transferred from the kettle’s heater's thermal energy store, to the water’s thermal energy.
• When car brakes are pressed, friction between the car’s brakes and the wheels of the car exerts a force that does work. Energy is transferred from the wheels’ kinetic energy stores to the thermal energy stores of the surroundings.
• When a cyclist hits a fence the normal contact force between the cyclist and the fence does work. Energy is transferred from the cyclist’s kinetic energy stores to other types of energy stores in the fence and surroundings.

1.1.2 Calculating Energy Transfers

Calculating Kinetic Energy

• The amount of kinetic energy stored in a moving object depends on two things: the mass of the object and the speed of the object.
• The faster an object moves or the larger the mass of the object, the more kinetic energy it stores. 
• The kinetic energy stored by a moving object can be calculated using the equation: \(E_{k} = \frac{1}{2} m v^{2}\) 
• \(E_{k}\) is the kinetic energy of the object and is measured in joules (J).
• \(m\) is the mass of the object and is measured in kilograms (kg).
• \(v\) is the speed of the object and is measured in metres per second (m/s).

Calculating Gravitational Potential Energy

• To raise an object above ground level work must be done which results in energy transferred into the object’s gravitational energy stores.
• Work has to be done to raise an object above ground level because of the Earth’s gravitational field pulling the object down.
• The amount of gravitational potential energy stored in an object raised above ground level depends on three things: the mass of the object, the height of the object above the ground and the strength of the gravitational field the object is in.
• The gravitational potential energy gained by an object raised above ground level can be calculated using the equation: \(E_{p} = mgh\)
• \(E_{p}\) is the gravitational potential energy of the object and is measured in joules (J).
• \(m\) is the mass of the object and is measured in kilograms (kg).
• \(g\) is the gravitational field strength and is measured in newtons per kilogram (N/kg).
• \(h\)is the height of the object and is measured in meters (m).

Calculating Elastic Potential Energy

• Stretching or compressing an object can transfer energy to the object’s elastic potential energy stores.
• Deformation is the change in the shape of an object from being stretched or compressed.
• Elastic objects are objects that return to their original shape after being deformed from stretching or compressing and store elastic potential energy.
• Inelastic objects are objects that do not return to their original shape after being deformed from stretching or compressing and do not store elastic potential energy.  
• The amount of elastic potential energy stored in a stretched spring can be calculated using the equation: \(E_{e} = \frac{1}{2} k e^{2}\) 
• is the elastic potential energy and is measured in joules (J).
• is the spring constant and is measured in newtons per metre (N/m).
• is the extension of the spring and is measured in meters (m).
• The elastic potential energy equation for a spring cannot be used once the spring’s limit of proportionality has been exceeded.

1.1.3 Specific Heat Capacity

What is Specific Heat Capacity?

• The specific heat capacity of a substance is the amount of energy required to raise the temperature of 1 kg of the substance by 1 °C.
• Specific heat capacity tells you how much energy is needed to heat up a substance.
• The larger the specific heat capacity of a material, the more energy needs to be transferred to the material’s thermal energy stores for the material to heat up.
• The larger the specific heat capacity of a material, the more energy is transferred out of the material’s thermal energy stores when the material is cooled down.

Calculating Specific Heat Capacity

• The amount of energy stored in or released from a system as its temperature changes can be calculated using the equation: \(\Delta E=mc\Delta \theta\)
• \(\Delta E\) is the change in thermal energy and is measured in joules (J).
• \(m\) is the mass of the substance and is measured in kilograms (kg).
• \(c\) is the specific heat capacity of the substance and is measured in joules per kilogram per degree Celsius (J/kg °C).
• \(\Delta \theta\) is the change in temperature of the substance and is measured in degrees Celsius (°C).

1. Acceleration: The rate at which an object’s velocity changes, often caused by a force acting on it.
2. Chemical Energy: The energy stored in the chemical bonds within substances such as fuels and batteries. It can be released and transformed into other forms like kinetic energy.
3. Charge: A measure of the amount of electric charge that flows in a circuit, measured in coulombs (C).
4. Current: The flow of electric charge around a circuit, measured in amperes (A).
5. DisplacementThe forced removal of people from their land.: The distance moved by an object in the direction of a force, measured in metres (m).
6. Elastic Potential Energy: The energy stored when an object such as a spring or rubber band is stretched or compressed.
7. Electrical Energy: The energy carried by electric currents and transferred when charges move through a potential difference.
8. Energy: The ability to do work or cause change, stored in different forms and transferred between stores.
9. Energy Store: A way that energy is kept within a system, such as kinetic, thermal, chemical, gravitational potential, or elastic potential.
10. Energy Transfer: The movement of energy from one store or system to another, such as by heating, mechanical work, or electrical work.
11. Extension / Stretch: How much a spring or elastic object is extended or compressed compared to its original length.
12. Force: A push or pull acting on an object that can cause acceleration, measured in newtons (N).
13. Gravitational Field Strength: A measure of the force of gravity on an object per kilogram of mass, measured in N/kg.
14. Gravitational Potential Energy: The energy stored in an object due to its height above the ground. The higher the object, the more gravitational potential energy it stores.
15. Heating: A process in which thermal energy is transferred from a hotter object to a cooler one.
16. Height: The vertical distance an object is raised above ground level, measured in metres (m).
17. Internal Energy: The total energy stored inside a system due to the movement and arrangement of particles.
18. Kinetic Energy: The energy an object has because it is moving. It increases with mass and speed.
19. Mass: The amount of matter in an object, measured in kilograms (kg).
20. Mechanical Work: Energy transferred when a force moves an object over a distance.
21. Object: A physical item or mass that can store or transfer energy.
22. Potential Difference: The energy transferred per unit charge when charge moves between two points in a circuit, measured in volts (V).
23. Power: The rate at which energy is transferred or work is done, measured in watts (W).
24. Rate: A measure of how quickly a change happens. In physics, power is the rate of energy transfer.
25. Specific Heat Capacity: The amount of energy needed to raise the temperature of 1 kg of a substance by 1 °C.
26. Speed: The distance an object travels per unit time, measured in metres per second (m/s).
27. Spring Constant: A measure of how stiff a spring is. A larger value means a stiffer spring.
28. System: An object or group of objects that can be studied as a single unit for energy analysis.
29. Temperature Change: The difference between the final and initial temperature of a system, measured in °C or K.
30. Thermal Energy: The internal energy stored in a substance due to the motion of its particles. It increases when a system is heated.
31. Voltage: Another term for potential difference, describing how much energy is transferred per unit charge.
32. Weight: The force acting on an object due to gravity.
33. Work Done: The amount of energy transferred when a force moves an object or when charge flows through a potential difference.