Unit 4 Mechanical Systems Topic 3 Energy, Friction, Efficiency

Kinetic energy – energy present in moving objects (joules) Potential energy – stored energy (joules) in an object that is “potentially available” There are many forms of potential energy.

Some forms of energy: Thermal energy (heat) = total energy of all moving particles in a substance or object Chemical energy = energy stored in foods and fuels Mechanical energy = energy associated with machines

Other Forms of Energy: Solar Energy Sound Energy Tidal Energy Gravitational Energy Light Energy Wind Energy

Energy converter = device that can convert energy from one form to another Energy transmitter = device where energy is transmitted from one place to another, but no energy is converted

E.x. The school bell converts chemical energy to mechanical energy to sound energy.

E.x. The mechanical mouse converts chemical energy (from our bodies) to mechanical energy.

What conversion happens in a solar heater? A solar heater converts light energy into heat energy. (or light into electrical)

What energy conversion takes place in a toy rocket? The rocket changes chemical energy to mechanical energy, heat energy, light energy and sound energy.

The efficiency of a machine tells you how much input energy was transferred to the load by the machine (output). Efficiency = output energy input energy

Every time a machine does work, some energy is lost due to friction (ex. blades on scissors rubbing together) Reducing friction (by adding lubricant such as oil or grease) makes machines more efficient.