Kinetic Energy (Edexcel International A Level Physics)
Revision Note
Kinetic Energy
Kinetic energy (usually written Ek and sometimes KE) is the energy an object has due to its motion (or velocity)
The faster an object moves, the greater its kinetic energy
When an object is falling, it is gaining kinetic energy since it is gaining speed
This energy transferred from the gravitational potential energy it is losing
An object will maintain this kinetic energy unless its speed changes
Kinetic energy can be calculated using the following equation:
Kinetic energy (KE): The energy an object has when it is moving
Derivation of Kinetic Energy Equation
A force can make an object accelerate; work is done by the force and energy is transferred to the object
Using this concept of work done and an equation of motion, the extra work done due to an object's speed can be derived
The derivation for this equation is shown below:
Worked Example
A body travelling with a speed of 12 m s–1 has kinetic energy 1650 J.
If the speed of the body is increased to 45 m s–1, estimate its new kinetic energy.
Answer:
Examiner Tips and Tricks
When using the kinetic energy equation, note that only the speed is squared, not the mass or the ½.
If a question asks about the ‘loss of kinetic energy’, remember not to include a negative sign since energy is a scalar quantity.
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