Topic 2.3: Work, Energy, and Power Flashcards
• 2.3.1: Outline what is meant by work
o WORK: Work is done when a force moves an object in the direction of the force. Work is a scalar quantity
Define joule
o JOULE: The unit of energy. The SI unit is the joule. 1J=1N*1m
• 2.3.2: Determine the work done by a non-constant force by interpreting a force-displacement graph
o WORK DONE BY A NON-CONSTANT FORCE: Work done is the area under the force-distance graph. Eg for Hooke’s law, W=½kx^2
Define energy
o ENERGY: The ability to do work.
• 2.3.4: Outline what is meant by kinetic energy
o KINETIC ENERGY: Energy an object has as a result of its motion.
• 2.3.5: Outline what is meant by change in gravitational potential energy
o GRAVITATIONAL POTENTIAL ENERGY: Energy an object has a result of its position in a gravitational field.
• 2.3.6: State the principle of conservation of energy
o PRINCIPLE OF CONSERVATION OF ENERGY: Energy is never created nor destroyed. It just changes from one form to another.
Define elastic collisions
o ELASTIC COLLISIONS: KE is conserved in these collisions. (Momentum is conserved in every collision).
Define explosive collisions
o EXPLOSIVE COLLISIONS: KE is increased in this collision
Define inelastic collisions
o INELASTIC COLLISIONS: The total KE is decreased. If the objects stick together, the collision is PERFECTLY inelastic.
Define power
o POWER: The rate of doing work. Unit is the watt. 1W=1Js-1
• 2.3.10: Define and apply the concept of efficiency
EFFICIENCY: Fraction of energy which is usefully transferred.
Efficiency=(useful work done)/(total work done)
