Everything Science Grade 10

CHAPTER 22. MECHANICAL ENERGY 22.2

EP= mgh = (1)(9,8)(2) = 19,6 J

EP= mgh = (1)(9,8)(0) = 0 J

The potential energy is a maximum.

The potential energy is a minimum.

Example 1: Gravitational potential energy

QUESTION

A brick with a mass of 1 kg is lifted to the top of a 4 m high roof. It slips off the roof

and falls to the ground. Calculate the gravitational potential energy of the brick at

the top of the roof and on the ground once it has fallen.

SOLUTION

Step 1:Analyse the question to determine what information is provided

• The mass of the brick ism= 1 kg


• The height lifted ish= 4 m

All quantities are in SI units.

Step 2:Analyse the question to determine what is being asked

• We are asked to find the gain in potential energy of the brick as
  it is lifted
  onto the roof.


• We also need to calculate the potential energy once the brick is
  on the
  ground again.
  Step 3:Use the definition of gravitational potential energy to calculate the
  answer

Physics: Mechanics 445