WORK+ENERGY+AND+POWER

IB Physics > Mechanics
 * 1 Measure || 2 Mech || 3 Therm || 4 Waves || 5 Electric || 6 Fields || 7 Atomic || 8 EPCC || 9 MIF || 10 Therm AHL || 11 Wave Phen || 12 EMI || 13 QNP || 14 Digital || OPT || PRAC || REVISE ||


 * KINEMATICS || FORCES AND DYNAMICS || WORK, ENERGY AND POWER || UNIFORM CIRCULAR MOTION ||

WORK, ENERGY AND POWER
Outline what is meant by work.

WORK: Work is done when a force moves an object in the direction of the force. Work is a scalar quantity. Where F is at angle θ to s:

JOULE: The unit of energy. The SI unit is the joule. 1J=1N*1m

Students should be familiar with situations where the displacement is not in the same direction as the force

Determine the work done by a non‑constant force by interpreting a force–displacement graph.

WORK DONE BY A NON-CONSTANT FORCE: Work done is the area under the force-distance graph. Eg for Hooke’s law, W=½kx2



A typical example would be calculating the work done in extending a spring. See 2.3.7.

Solve problems involving the work done by a force.

ENERGY: The ability to do work.

Outline what is meant by kinetic energy.

KINETIC ENERGY: Energy an object has as a result of its motion. Outline what is meant by change in gravitational potential energy. GRAVITATIONAL POTENTIAL ENERGY: Energy an object has a result of its position in a gravitational field.

State the principle of conservation of energy.

PRINCIPLE OF CONSERVATION OF ENERGY: Energy is never created nor destroyed. It just changes from one form to another. List different forms of energy and describe examples of the transformation of energy from one form to another. Distinguish between elastic and inelastic collisions. ELASTIC COLLISIONS: KE is conserved in these collisions. (Momentum is conserved in every collision). INELASTIC COLLISIONS: The total KE is decreased. If the objects stick together, the collision is PERFECTLY inelastic. EXPLOSIVE COLLISIONS: KE is increased in this collision.

Students should be familiar with elastic and inelastic collisions and explosions. Knowledge of the coefficient of restitution is not required.

Define power. POWER: The rate of doing work. Unit is the watt. 1W=1Js-1 Define and apply the concept of efficiency.

EFFICIENCY: Fraction of energy which is usefully transferred. Efficiency=Useful work done/ Total work done Solve problems involving momentum, work, energy and powe r.