Motion plus position
Mechanical energy.
Two kinds of energy
A flying cricket ball has energy because it is moving. A flowerpot on a high shelf has energy because of where it is.
How do you think we can describe the total mechanical energy of an object?
What this lesson covers
The idea
Mechanical energy is the energy an object possesses due to its motion or position; it is the sum of the object's kinetic energy and potential energy.
Two kinds of energy
A flying cricket ball has energy because it is moving. A flowerpot on a high shelf has energy because of where it is.
How do you think we can describe the total mechanical energy of an object?
- Add the two kinds of energy
- Subtract one from the other
- Take the larger one
Add the bars
Set the two kinds of energy and read the total.
The sum
The bars added up. Energy due to motion is kinetic energy, and energy due to position (or shape) is potential energy. Their sum is the mechanical energy.
Mechanical energy is the energy an object possesses due to its motion or position. It is the sum of its kinetic energy and its potential energy.
Notes
Mechanical energy = energy due to motion or position = kinetic energy + potential energy.
Check yourself
An object has kinetic energy 25 J and potential energy 15 J. What is its mechanical energy, in J?
Answer: 40 J
25 J + 15 J = 40 J.
Mechanical energy is the energy an object has due to its…
Mechanical energy is…
A ball at rest on a high shelf has no kinetic energy and 40 J of potential energy (an example). What is its mechanical energy, in J?
Answer: 40 J
0 J + 40 J = 40 J.
- colour or size. Colour and size do not define mechanical energy. It comes from the motion or the position of the object.
- temperature. Mechanical energy comes from motion or position, not from temperature.
- motion or position — correct. Yes!
- kinetic energy + potential energy — correct. Yes!
- kinetic energy − potential energy. The two are added, not subtracted.
- kinetic energy × potential energy. The two are added, not multiplied.