Work is done when a force acts on an object and causes it to move in the direction of the force.
Work done = force × displacement in the direction of the force.
5.1.2 Conservation of energy:
The principle of conservation of energy states that energy cannot be created or destroyed but can only be transferred or transformed from one form to another.
The total energy of a closed system remains constant.
5.1.3 Efficiency:
Efficiency is the ratio of useful energy output to the total energy input in a system.
Efficiency = (useful energy output / total energy input) × 100%.
5.1.4 Power:
Power is the rate at which work is done or energy is transferred.
Power = work done / time taken.
Power is also given by the formula P = Fv, where P is power, F is the force applied, and v is the velocity of the object.
5.2 Gravitational potential energy and kinetic energy:
5.2.1 Gravitational potential energy:
Gravitational potential energy (EP) is the energy possessed by an object due to its position in a gravitational field.
The change in gravitational potential energy (∆EP) is given by
∆EP = mg∆h, where m is the mass of the object, g is the acceleration due to gravity, and ∆h is the change in height.
5.2.2 Kinetic energy:
Kinetic energy (EK) is the energy possessed by an object due to its motion.
The formula for kinetic energy is EK = 1/2mv2, where m is the mass of the object and v is its velocity.