Conservation of energy / work energy principle

Section 1: Understanding Conservation of Energy

Get to know the law of conservation of energy, which states that energy cannot be created or destroyed, only converted from one form to another.
Apply this principle to mechanical systems to deduce that the total mechanical energy (the sum of kinetic and potential energy) of a system remains constant if only conservative forces (like gravity) are in play.
Understand that if non-conservative forces (like friction) are present, the mechanical energy of the system will decrease, as part of it is converted into heat or sound.

Section 2: Kinetic Energy and Potential Energy

Be able to calculate kinetic energy with the formula 1/2 m v^2, where “m” is mass and “v” is velocity.
Understand that potential energy is the energy stored in an object because of its position within a force field such as gravity. The formula for gravitational potential energy is m g h, where “m” is mass, “g” is gravitational acceleration and “h” is height.
Familiarise yourself with how mechanical energy transfers between these two forms as an object moves in gravitational field: as an object rises, its kinetic energy decreases while its potential energy increases, and vice versa.

Section 3: The Work-Energy Principle

Learn that the work-energy principle states that the work done on an object is equal to the change in its kinetic energy.
Remember that work done is calculated as the force applied on the object multiplied by the distance over which the force is applied (in the direction of the force). The formula is work = force x distance.
Recognise that if the work done on an object is positive, its kinetic energy increases (it speeds up); if the work done is negative, its kinetic energy decreases (it slows down).
Understand that external forces, like friction or a pushing force, can do work on a system, changing its total mechanical energy.

Section 4: Power and Efficiency

Familiarize yourself with the concept of power, which is work done per unit time. The formula for power is power = work/time.
Understand that in real systems, not all the work done will be used effectively due to losses like friction. Therefore, no machine is 100% efficient.
Calculate efficiency using the formula efficiency = (useful output energy/work input) x 100%. A machine’s efficiency is always less than 100% as some energy is always wasted in overcoming friction or air resistance.

Make sure to apply these concepts when working through problems, remembering to include the appropriate units in your calculations and being aware of potential sources of error, such as friction or air resistance.