CH 7: Energy

• Work done on an object is defined as the product of force acting on the object and distance traveled in the direction of the force.
• The formula for work done is W = F * S.
• Work is a scalar quantity, with the unit of measurement being Joules (J).
• No work is done when an object is not moved, as there is no distance traveled.
• Energy E is the ability to do work and is a scalar quantity, with the unit of measurement being Joules (J).
• There are nine common types of energy: gravitational potential energy, kinetic energy, thermal energy, solar or light energy, sound energy, electrical energy, nuclear energy, elastic potential energy, and chemical potential energy.
• Gravitational potential energy is energy stored by objects that are in high places.
• Kinetic energy is the energy processed by an object due to its motion.
• Thermal energy is internal energy that is responsible for the temperature of an object.
• Solar or light energy is the energy that is produced by illuminating an object.
• Climbing up with a rope reaches the top of the building faster but is more tiring because it draws energy at a shorter period of time, hence the rate of energy, which is power, is greater.
• Climbing up with staircase reaches the top of the building slower but is less tiring because it draws energy at a longer period of time, hence the rate of energy, which is power, is lower.
• Efficiency can also be defined as the ratio of useful power output to power input.
• Power equals work done over time taken or W over T.
• The SI unit for power is W.
• If efficiency is expressed in percentage, it can be multiplied with hundred percent.
• Efficiency in practice is the measure of how efficiently an isolated system is able to convert energy input into useful energy output.
• Efficiency is defined as the ratio of useful energy output to energy input and has no unit.
• Power is inversely proportional to time but energy is independent of time.
• An ideal 100% efficient system means all energy input has been converted into useful energy output.
• Sound energy is the energy that is caused by vibrating objects.
• Electrical energy is the energy that is caused by moving electrical charges.
• Nuclear energy is the energy released from atoms either by nuclear fusion or nuclear fission.
• Elastic potential energy is the energy stored as a result of applying a force to deform an elastic object.
• Chemical potential energy is the energy that can be stored and released chemically, for example, food batteries or fuel.
• Gravitational potential energy (GPE) is the energy processed by an object due to its position in a gravitational field.
• Kinetic energy (KE) is the energy processed by an object due to its motion.
• Thermal energy (THERMAL_ENERGY) is internal energy that is responsible for the temperature of an object.
• Solar or light energy (SOLAR_ENERGY) is the energy that is produced by illuminating an object.
• Sound energy (SOUND_ENERGY) is the energy that is caused by vibrating objects.
• Electrical energy (ELECTRICAL_ENERGY) is the energy that is caused by moving electrical charges.
• Nuclear energy (NUCLEAR_ENERGY) is the energy released from atoms either by nuclear fusion or nuclear fission.
• Elastic potential energy (ELASTIC_POTENTIAL_ENERGY) is the energy stored as a result of applying a force to deform an elastic object.
• Chemical potential energy (CHEMICAL_POTENTIAL_ENERGY) is the energy that can be stored and released chemically, for example, food batteries or fuel.
• The principle of conservation of energy states that the total energy of an isolated system remains constant.
• In the principle of conservation of energy, when a bob is released at point a, the initial speed is zero, the maximum kinetic energy (KE) is zero, and the maximum gravitational potential energy (GPE) is equal to the initial kinetic energy (KE).
• When the bob reaches point b, the speed is maximum, the maximum kinetic energy (KE) is zero, and the maximum gravitational potential energy (GPE) is equal to the initial kinetic energy (KE).
• The change in kinetic energy (KE) of the bob is calculated as KE = GPE - GPE1, resulting in a change in KE of 0 joules.
• Power is the rate of work done or energy transferred.
• When the pendulum swings, some energy is converted to heat due to air resistance, which is considered waste energy.