This topic will look at Kinetic Energy, which follows our previous posts on Energy Stores and Work done. You can view those topics here:

Energy Stores • GCSE Physics & Science Revision Notes for Exams
We use energy to fuel movement and light, which can be found in various forms, such as light waves, heat waves, sound waves and kinetic energy. When we use energy, it is not destroyed but transferred from one entity or energy source to another.
Work Done • GCSE Physics & Science Revision Notes for Exams
Energy can be transferred from one object to another by doing work. When we say work is done, it means that force is applied to an object, and that force moves the object over a distance.
Energy Stores: Revision Quiz
Learning and revising the topic of energy stores can be daunting, but it can become more manageable with the right tools and knowledge. These questions are designed to help students understand and learn the fundamental concepts of energy stores.

You may recall that energy is a fundamental property of the universe. According to the law of energy conservation, energy can never be created or destroyed, only transferred or converted from one form to another. This means energy is never used up or lost; instead, it is transferred between different energy stores and objects.

For example, consider a light bulb. When you turn on a light bulb, electrical energy is transferred from the power source to the bulb, where it is converted into light and thermal energy. The light energy illuminates the surroundings, while the thermal energy dissipates into the surrounding environment as heat. When you turn off the light bulb, the energy is not destroyed but rather is transferred back to the power source or the environment.
Another example is a moving object, such as a ball. When you throw a ball, you transfer energy from your muscles to the ball, giving it kinetic energy. As the ball moves through the air, it loses some of its kinetic energy to the air due to friction, causing it to slow down. However, the kinetic energy lost by the ball is not destroyed but instead transferred to the air as thermal energy.

In both examples, energy is not used up or lost but transferred or converted into other forms of energy. This is true for all energy transformations, whether in a chemical reaction, a mechanical system, or an electrical circuit.

Now that you've got your head around energy stores, it's time to see how you can calculate the amount of energy in Kinetic, Gravitational Potential and Elastic Potential energy stores.

Kinetic energy stores

Kinetic energy is one of the many forms of energy that objects can possess. The other energy stores include potential, thermal, chemical, nuclear, and electromagnetic energy. Each energy store represents a different way in which energy can be stored or transferred.

Kinetic energy is a type of energy an object possesses due to its motion. When an object is in motion, it has the potential to do work or cause change. Kinetic energy is the energy that is associated with this motion and is dependent on the object's mass and velocity (speed).

So, Kinetic Energy is the energy that an object possesses when it is in motion. Any moving object has kinetic energy; the faster it moves, the more kinetic energy it has.

The formula for calculating kinetic energy is:

\(\mathrm{E}_{\mathrm{k}}=\frac{1}{2} \mathrm{mv}^2\)

In plain English, Kinetic Energy (KE) equals = \(\frac{1}{2}\) (multiplied by)  Mass (m) × (multiplied by) Velocity squared (v²)

This means that kinetic energy is directly proportional to an object's mass and the square of its velocity.

For example, consider a car moving at a speed of 50 miles per hour (mph) and a bicycle moving at a speed of 10 mph. The car has a greater mass than the bicycle, requiring more force to set it in motion. The car, therefore, has a higher kinetic energy than the bicycle.
Kinetic Energy diagram using a car as an example

Now, let's look at the same car moving at different speeds. Suppose the car initially moves at 50 mph and then accelerates to 100 mph. At 100 mph, the car has four times as much kinetic energy as it did at 50 mph, even though its speed has only doubled.

Kinetic Energy Example of Ball Being Thrown

Another example of kinetic energy is a ball being thrown. When you throw a ball, it has kinetic energy because it is in motion. The harder you throw the ball, the more kinetic energy it has. This kinetic energy is transferred to another object when the ball collides with it, such as a wall or a person's hand.

So, a car of mass 3000 kg is travelling at 30 m/s. What would be in the kinetic energy store?

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