work energy and power ss1 physics
work is defined as a force causing the movement or displacement of an object.
Work done is defined as the product of force and the displacement in the direction of force.
work = F × S
WORK= FORCE(NEWTON) ×DISPLACEMENT(METRES)
The magnitude of work done is given by
Work Done= force×distance
The unit of work is joules.
A girl of mass 80kg runs up a set steps of total height
7.0m . Find the work done against gravity.
work done = mgh
Energy is the capacity to do work. It is measure in joules.
FORMS OF ENERGY
- Mechanical energy
- Heat energy
- Light energy
- Chemical energy
- Electrical energy
- Atomic energy
- Solar energy
TYPES OF MECHANICAL ENERGY
Mechanical energy is categorize into two types, which are:
- Potential energy
- Kinetic energy
Potential energy is the energy possessed by a body due to its position or state.
A body may posses a potential energy due to its position in a force field . If the force field is the gravitational field,the body is said to have gravitational potential energy.
where g is acceleration due to gravity,
m is mass and h is height above the ground.
Egp is gravitational potential energy.
Examples of Potential energy are:
- An electric charge at rest in an electric field.
- A magnet at rest in magnetic field.
- When petrol,wood, or kero is burn.
Kinetic energy (K.E) is the energy possessed by a body due to its motion.
Example of kinetic energy are :
- A boy running a race.
- Air or wind in motion.
- Electrical charges in motion.
- A body or an object falling under gravity.
The kinetic energy(K.E) of a body in motion is giving by
Where m is the mass and v is the velocity.
PROBLEM ON KINETIC ENERGY
An object of mass 8kg is moving at velocity of 20ms¯²
K.E= ½ ×8×20²
Power is defined as the rate at which work is done.