Quantity Symbol Unit Comments
Mass M kilogram kg
Volume V metres cube m³

Area x Height
Density r kg/m³

density of air (sea level) 1.29 kg/m3

density of water 1g/cm3 at 4oC
Force F Newtons N
Weight W Newtons N Weight is a Force
Moment M Newton metres Nm Moment of a turning force
Distance D metre m
Time t second s
Acceleration a metres per second squared  m/s² Rate of change of velocity/speed with time
Kinetic Energy Ek Joules J Energy due to motion
Potential Energy PE Joules J Stored Energy when the object is at rest
Speed V meters per second m/s

 

Speed of light in vacuum is approximately 3 x 108 m/s 

Speed of sound in air at 0°C is approximately 330 m/s

Rate of change of distance with time.

Scalar quantity (size only)
Velocity V meters per second m/s

Vector quantity (size and direction)

In some questions an examples Speed and Velocity mean the same thing. 
Initial speed/velocity u m/s Speed from rest
Final speed/velocity v m/s Speed at end
Wavelength l metre m One complete waveform
Frequency F Hertz hz
Gravity g metres per second squared  m/s² Acceleration due to gravity is 9.81 m/s²
Work W Joules J
Power P Watts W This is not the same as Volt-Amps
Voltage V Volts V This is the potential difference across a device
Current I amps A Flows through a device
Resistance R ohms W Resistance offered to the flow of current


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