The Concept of Work
The S.I Unit of Work
- Chemical energy
- Heat energy
- Light energy
- Sound energy
- Electrical energy
- Nuclear energy
- Solar energy
Difference between Potential Energy and Kinetic Energy
Distinguish between potential energy and kinetic energy
There are two types of chemical energy, which are:
Potential energy:It is the energy possessed by a body mass in its position or state.
Kinetic energy: It is the energy possessed by a body due to its motion.
The Transformation of Energ
The notion of energy is that energy is changed from one form into different forms using transducers.
Transducer is a device used to transform energy from one form to another.
Battery converts chemical energy into electrical energy.
A generator converts mechanical energy into electrical energy.
A motor converts electrical energy into mechanical energy.
The Table Summarising Energy Transformation
|ORIGINAL ENERGY||TRANSDUCER||ENERGY TRANSFORMED|
|Chemical energy||Battery||Electrical energy|
|Chemical energy||Motor||Chemical energy|
|Mechanical energy||Generator||Electrical energy|
|Solar energy||Solar panel||Electrical energy|
|Chemical energy||Motor car||Mechanical energy|
|Electrical energy||Microphone||Sound energy|
|Electrical energy||Heater||Heat energy|
A heavy stone
A bucket full of water
A strong inelastic rope; and
Collect the heavy stone, using a strong rope tie it to a bucket of water
Pass the rope over smooth pulley fixed to a support.
Hold stationary the heavy stone at height “h” above the ground
Release the stone
When the stone released the bucket of water will start to rise.
The stone is said to have potentials energy because of its position above the ground.
Lifting a body of mass “m” to a height “h” above the ground requires work to be done against gravity. Work = Mgh
- Pull the bob of a simple pendulum in position A so that it is at height “h” above position B.
- Release the bob so that it swings to position C via the lowest position B and back to A.
- Consider the figure below:
- The bob has Vmax and hence K.Emax at B. The height at B is zero, thus the P.E is zero.
- As it swings towards C, the P.E increases and reaches its maximum again in position C, where the Kinetic Energy is zero. At position D, the energy of the bob is party potential and party Kinetic.
The Principle of Conservation of Energy
Uses of Mechanical Energy
The Concept of Power
- It is a measure of the rate at which energy changes.
- This means that whenever work is done energy changes into a different form.
State the S.I unit of power
The Rate of Doing Work
Determine the rate of doing work
Work done = GPE
The power of crane A can be calculated by;
The power required is given by:
Since work causes a change in energy. DE power can be considered as the rate of change of energy.
P = DE/t