Work, Energy Power

Textbook chapter 5

Work done

• Work done = force × distance moved in the direction of the force

• W=Fx

• Units: joules(J, =Nm)

Gravitational potential energy

• E_p = mgh

• The capacity for doing work as a result of an objects position in a gravitational field

• Units: joules(J, =Nm)

Kinetic energy

• E_k = ½ mv²

• Energy associated with an object as a result of its motion

• Units: joules(J, =Nm)

• E_k α m

• E_k α v²

Power

• Rate of work done

• P=W/t

• P=E/t

• Units: watts(W, =Js^-1)

Efficiency

• Efficiency = (useful output energy) / (toatal output energy) × 100

Smooth surface

The principle of conservation of energy

The total energy of a closed system remains constant - energy cannot be created nor destroyed

Deriving the equation for kinetic energy