CIE A Level Physics复习笔记5.2.2 Kinetic Energy
Derivation of KE = 1/2mv2
- Kinetic energy is energy an object has due to its motion (or velocity)
- 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:
Derivation for Kinetic Energy equation
Kinetic Energy
- Kinetic energy is energy an object has due to its motion (or velocity)
- The faster an object is moving, 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
Equation for Kinetic energy
KE: The energy an object has when its moving
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, what is its new kinetic energy?
Exam Tip
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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