ENERGY Energy Energy is the ability to do work It is measured in Joules (J) Energy Forms G – Gravitational potential energy L – Light energy E – Elastic energy U– E – Electrical energy N – Nuclear Energy K – Kinetic energy C – Chemical energy S – Sound energy H – Heat energy LAW OF CONSERVATION OF ENERGY Energy cannot be created or destroyed, only change from one form to another. Energy Sources Renewable – Resources that are replaced by nature in less than a human lifetime Non -Renewable – Resources that are used faster than they can be replaced by nature Examples: solar, wind and hydroelectric Examples: Fossil Fuels and Nuclear power POTENTIAL ENERGY EQUATION PE = mgh •m is mass (kg) •g is the gravitational 2 constant (N/m ) •h is the height (m) POTENTIAL ENERGY Investigation Location Chair Table Height (m) P.E (J) Fair test: • Only change one thing • Keep the mass the same Head 1 Head 2 Above your head • Change the height • g will remain constant POTENTIAL ENERGY AGAINST HEIGHT GRAPH • Directly proportional • Straight line • Goes through the origin Potential Energy This is the energy an object has because of its position in a gravitational field. The amount of gravitational potential energy an object has depends on its mass, its height above the ground and the strength of the gravitational field. Things to think about What would happen if we changed the mass and kept the height constant Why does a bigger mass have more potential energy What would happen if you measured the potential energy of an object at 1m off the ground on earth compared to on the moon? KINETIC ENERGY EQUATION 1 2 KE = m 2 v •m is mass (kg) •V is velocity (m/s) KINETIC ENERGY Investigation Time (S) Velocity (m/s) V2 (m/s) K.E (J) Fair test: • Only change one thing • Keep the mass the same • Keep distance the same • Only change velocity Kinetic Energy Kinetic energy is the energy an object has because it is moving. The amount of kinetic energy an object has depends on its mass, and on its speed or velocity Things to think about What would happen if we changed the mass and kept the velocity constant Why does an object with a larger mass have more kinetic energy than a smaller object Work done Work done is the amount of energy changed from one form to another. We can find out how much work is done by finding how much energy has changed. WORK DONE Work = F x d •F is the force (N) •d is the distance (m) Power Power is the rate at which work is done or energy is used. Power is measured in joules per second (J/s) or watts (W). POWER ππππ ππππ πππ€ππ(π) = π‘πππ π‘ππππ πΈπππππ¦ πππ€ππ(π) = π‘πππ π‘ππππ πΉπ₯π πππ€ππ(π) = π‘ MEASURING PERSONAL POWER Method: • Run up a flight of stairs • Get someone to time you • Weigh yourself to find out your weight • Measure the height of the stairs • Use power equation to find your person height • https://www.bbc.co.uk/bites ize/guides/zkrg6v4/revision /1 MEASURING THE OUTPUT POWER OF AN ELECTRIC MOTOR Method: • Add weights to the string attached to the motor • We will then record how long it takes to travel past two points • Repeat with different weights • Calculate the power of the motor Output power of a motor Weight (N) Height (m) Work done (J) Time 1 (s) Time 2 (s) Time 3 (s) Avg time (s) Average Power (W) Efficiency Efficiency is the ratio of the output to the input. Efficiency tells us how much of the input energy is transferred in the intended way – useful energy compared to total energy. Efficiency is expressed as a percentage by multiply the ratio by 100 EFFICIENCY Efficiency = πΈπππππ¦ ππ’π‘ππ’π‘ πΈπππππ¦ ππππ’π‘ Efficiency= πππ€ππ ππ’π‘ππ’π‘ πππ€ππ ππππ’π‘ Efficiency= πΈππ’π‘ πΈππ or πππ’π‘ πππ
