# Pressure, Work, Energy and Power

Time for some more equations:

Pressure (Pa)

Force (N)

Area (m^{2})

Work = Force x Distance moved in the direction of the force

Work (J)

Force (N)

Distance moved (m)

Where Work Done = Energy Transferred

Note that 1 Joule = 1 Nm

Energy

Kinetic Energy = ½ x mass x velocity^{2}

Kinetic Energy (J)

Mass (kg)

Velocity (ms^{-1})

Change in Gravitational Potential Energy = mass x gravitational field strength x change in height

Gravitational field strength = 9.81 NKg^{-1}

Change in Gravitational Potential Energy (J)

Note that often questions rely on the principal that

Change Kinetic Energy = Change in Gravitational Potential Energy

Questions involving kinetic energy being transferred to gravitational
potential energy

**Example**

A helicopter of mass 800kg at a height of 1500m loses power and begins
to fall; assuming the speed of the helicopter at the top of its flight
is zero what is its speed on impact. Assume air resistance is negligible
and the gravitational field strength is 9.81.

Ep = mgh

Ep = 800 x 9.81 x 1500

Ep = 11772000 J

Ek = 11772000

11772000 = ½ x 800 x v^{2}

v = 171.55 ms^{-1}

Power

Power (W or Js^{-1})

**Definition**

Joule – The amount of work done when a force of one Newton moves
a distance of one meter in the direction of the force.

**Reference Tools**

Dictionary

Thesaurus

Maps

Scientific Calculator

Periodic Table

Translator

Unit Conversion

**Module 1**

Useful Physics Resources

Scalars, Vectors & Graphs

Fundamental Equations and Complex Vector Equations

Equations of Motion

Moments

Pressure, Work, Energy and Power

Deformation of Solids

Car Safety