Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Energy is defined as the capacity to do work and is measured in Joules ().
The Law of Conservation of Energy states that energy cannot be created or destroyed, only transformed from one form to another or transferred between objects. The total energy in a closed system remains constant ().
Kinetic Energy () is the energy of an object due to its motion. It depends on the mass () and the square of the velocity ().
Gravitational Potential Energy () is the energy stored in an object due to its height above a reference point. It is calculated using mass (), gravitational acceleration (), and height ().
Energy Transformation refers to the change of energy from one form to another (e.g., a battery converting chemical energy into electrical energy).
Heat is the transfer of thermal energy from a system at a higher temperature to one at a lower temperature until thermal equilibrium is reached.
Efficiency is a measure of how much 'useful' energy is produced compared to the total energy input. No machine is efficient as some energy is always dissipated as waste heat ().
📐Formulae
💡Examples
Problem 1:
A ball is held at a height of above the ground. Calculate its Gravitational Potential Energy (). (Assume )
Solution:
Explanation:
Using the formula for potential energy, we multiply the mass, the acceleration due to gravity, and the height to find the energy stored in the object.
Problem 2:
An electric motor takes in of electrical energy. It produces of useful mechanical work. What is the efficiency of the motor?
Solution:
Explanation:
Efficiency is calculated by dividing the useful output energy by the total input energy and multiplying by to get a percentage. The remaining is likely lost as heat.
Problem 3:
A toy car with a mass of is moving at a velocity of . Calculate its Kinetic Energy ().
Solution:
Explanation:
Applying the kinetic energy formula, we square the velocity first (), then multiply by the mass and the factor of .