Review the key concepts, formulae, and examples before starting your quiz.
🔑Concepts
Energy is the ability to do work. It exists in various forms and can be changed from one form to another.
Work is done when a force () is applied to an object and the object moves through a distance (). If there is no movement, no work is done.
Renewable Energy Sources: These are natural resources that can be replenished or replaced over a short period. Examples include Solar energy from the , Wind energy, and Hydro energy (from flowing water).
Non-renewable Energy Sources: These are resources that exist in limited amounts and take millions of years to form. Once used up, they cannot be replaced easily. Examples include fossil fuels like Coal, Petroleum, and Natural Gas ().
Solar Energy: The energy received from the in the form of heat and light. It is a clean and infinite source of energy.
Conservation of Energy: We must save energy because non-renewable sources are depleting fast. Simple acts like switching off lights help in conserving energy.
📐Formulae
💡Examples
Problem 1:
If a person applies a force of to push a cart and moves it by , calculate the work done.
Solution:
Explanation:
Work is the product of Force and Distance. Here, and , so the work done is units of energy (Joules).
Problem 2:
A student pushes a heavy wall with a force of for , but the wall does not move (). How much work is done?
Solution:
Explanation:
In science, work is only considered 'done' if the object moves. Since the distance , the total work done is zero regardless of the force applied.
Problem 3:
Identify which of the following is a renewable source of energy: Coal, Wind, or Petroleum.
Solution:
Wind is a renewable source of energy.
Explanation:
Coal and Petroleum are fossil fuels that take millions of years to form and are exhaustible. Wind is always available in nature and can be used repeatedly without running out.