1.1 - Energy Changes in a System

Flashcards covering fundamental concepts related to energy changes in a system for AQA Physics GCSE.

What is the equation for kinetic energy?

½ m v² (where m is mass in kg and v is velocity in m/s) where Energy is in Joules (J).

What is the equation for elastic potential energy?

½ k x² (where k is the spring constant in N/m and x is the extension in m) where Energy is in Joules (J).

What is the equation for gravitational potential energy?

mgh (where m is mass in kg, g is gravitational field strength in N/kg, and h is height in m) where Energy is in Joules (J).

Define the 'Specific Heat Capacity' of a substance.

The amount of energy needed to raise the temperature of 1 kilogram of a substance by 1 degree Celsius.

What are the units for Specific Heat Capacity?

Joules per degree Celsius per kilogram (J/°C/kg).

What is the definition of 'Power'?

The rate at which energy is transferred or the rate at which work is done.

State two equations for power.

1. Power = energy transferred/time (with Energy in Joules and Time in seconds). 2. Power = work done/time (with Work Done in Joules and Time in seconds).

What is the unit of power?

Watt (W).

Which motor dissipates the most power, Motor A or Motor B if Motor A lifts the same mass in half the time as Motor B?

Motor A dissipates the most power, as the energy transferred is the same but the time taken is less.

Describe the energy changes when a ball is thrown upwards and then returns to its starting position.

Upwards: KE is converted to GPE; Peak: Maximum GPE, zero KE; Downwards: GPE is converted back to KE.

Describe the energy transfers for a bungee jumper.

When falling, GPE is converted to KE; as the cord tightens, KE is converted and stored as Elastic Potential Energy (EPE); at the lowest point, the jumper’s initial GPE equals the EPE stored in the cord.

Explain why a bungee jumper slows down once the cord begins to stretch.

Kinetic energy decreases since it is converted to elastic potential energy; as KE decreases, so does velocity due to KE being proportional to velocity squared.

Give examples of chemical energy stores.

Food, fuel (wood, coal, petrol), and batteries.

State 4 different stores of energy.

1. Kinetic Energy 2. Gravitational Potential Energy 3. Elastic Potential Energy 4. Chemical Energy.