Momentum & Impulse with Vectors (Edexcel A Level Further Maths): Revision Note

Impulse-Momentum Principle with Vectors

How do impulse and momentum work in 2D?

• Impulse and momentum can be used in 2D as they are vector quantities

  • Impulse in 2D essentially works the same way as impulse in 1D

• For a constant force given by the vector  N acting on a particle for  seconds the impulse is given by the vector:

  •  

  • The units are still N s  (equivalent to kg m s^-1 )

• For a particle of mass  the impulse is still equal to the change in momentum

  •   or 

  • where u m s^-1 is the initial velocity vector and v m s^-1 is the final velocity vector

  • are all vector quantities, and is a scalar

  • If using column vectors, this equation would look as follows:

    • 

How are questions different in 2D?

• You could be asked to work out the magnitude of the impulse

  • You would need to find the two components of the impulse vector and then use Pythagoras

• You could be asked to work out the direction of the impulse

  • You would need to find the two components of the impulse vector and then use SOHCAHTOA (right-angled trigonometry)

  • You might need to find the angle between the impulse and the vector or  so always draw a sketch

• If you know the magnitude and direction of the impulse or a velocity, then you might have to resolve it into horizontal and vertical components