Work and Energy - Class 4 Notes & Olympiad Questions

Work and Energy

Work

a) Work is a term that describes the effort or energy used to move something or change its position. It's kind of like when you push or pull something and it moves because of your effort.
b) If you push or pull the box and it moves, you are doing work on the box. The amount of work you do depends on two things: how much force you use and how far you move the box.
c) Also, if you push or pull on something but it doesn't actually move, no work is being done either. So, work happens when you use force to make something move.

Energy

a) Energy is what enables us to do work. It's the ability to make things happen or make changes in the world around us.
b) The interesting thing about energy is that it can't be created, and it can't just disappear. It can transform from one form to another, but the total amount of energy always stays the same. So it's always conserved.

Types of Energy

We need energy to do all sorts of things like pushing, pulling, and moving objects. Energy comes in different forms like when we move, use electricity, feel the heat, see light, hear the sound, use batteries, or play with magnets.

There are two types of energy we should know about potential energy and kinetic energy.

1. Potential Energy

a) Potential energy is stored energy that an object has because of where it is or how it's positioned.
b) For example, a ball placed up high has more potential energy because it can fall down. Water stored in a dam or a stretched rubber band also has potential energy.

2. Kinetic Energy

a) Kinetic energy is the energy an object has because it's moving.
b) When something rolls down a hill, a car drives on the road, or an aeroplane flies in the sky, they all have kinetic energy.
c) The faster something moves, the more kinetic energy it has. When something stops moving, it doesn't have kinetic energy anymore, like when we stop walking or running, or when a car stops moving.

3. Energy Conversion

a) Muscular energy is what allows us to move and do physical activities, and it comes from the chemical energy stored in the food we eat. Similarly, when we drive a car, the fuel's chemical energy is turned into mechanical energy, which makes the car move.
b) Hydroelectric power plants use the energy from falling water to create electricity by using special machines called turbines and generators.
c) Windmills are another type of machine that converts the energy from moving air (wind) into electricity.
d) Solar energy is extremely important for all living things on Earth. Scientists and engineers are working on ways to capture solar energy and use it to generate electricity and heat for our everyday devices and appliances. For example, solar panels placed on rooftops can capture the sun's energy and turn it into electrical energy that we can use.