Work, Energy and Power

5.1 Energy conservation:

5.1.1 Work:

• 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 ∆E_P = 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 E_K = 1/2mv², where m is the mass of the object and v is its velocity.