Mechanical Energy

Mechanical Energy

By Mr Eko

Kinetic Energy

Work Example

Calculate the kinetic energy stored in a vehicle of mass 1200 kg moving at a speed of 27 m/s.

Gravitational Potential Energy

Worked Question

A man climbs a flight of stairs that is, in total, 3.0 m higher than the floor. The man has a mass of 72 kg, and the gravitational field strength on Earth is approximately 9.8 N/kg. Calculate the energy transferred to the man's gravitational potential energy store.

Mechanical Energy

​When the roller coaster is at rest on top of the hill, it has the maximum potential energy but zero kinetic energy. Because mechanical energy is the sum of both, the value of the potential energy is also the total mechanical energy.

Position 1

​When the roller coaster starts moving downward, it will start to speed up. The process of gaining speed means that kinetic energy is increasing.

This is what transformation of energy looks like. Some potential energy was transformed into kinetic energy when the roller coaster started moving. Adding the amount of potential and kinetic energy at every point in the roller coaster's motion give you the same amount of mechanical energy

Position 2

​The mechanical energy within this system is the same at any point

​Falling Object

Pendulum

Work Example

Multiple Choice

A cyclist travels down a hill from rest at point X, without pedalling. The cyclist applies his brakes and the cycle stops at point Y. Which energy changes have taken place between X and Y?

• gravitational potential → kinetic → thermal (heat)

• gravitational potential → thermal (heat) → kinetic

• kinetic → gravitational potential → thermal (heat)

• kinetic → thermal (heat) → gravitational potential

Multiple Choice

A car is stationary at the top of a hill with the engine switched off. The brakes are released and the car rolls down the hill. At which labelled point does the car have the greatest kinetic energy? Ignore friction

• A

• B

• C

• D

Fill in the Blanks

Fill in the Blanks