How do you calculate change in momentum?

Force and momentum question?

• The velocity of a vehicle of mass 600kg was reduced from 15m/s by a constant force of 400N which acted for 20s then by a constant force of 20N for a further 20s. a) sketch the force v. time graph (i can do this) bi) calculate the initial momentum of the vehicle ii) use the force v time graph to determine the total change of momentum iii) hennce show that the final velocity of the vehicle is 1m/s

• Answer:

  i. momentum = mass*velocity initial momentum = 600*15 = 9000 kg m/s ii. the momentum is the area underneath the graph (as you are doing force*time = momentum) to do this, you could make triangles and squares out of the area underneath, and use the area formulas for them to work out the total area. iii. once you have the change in momentum, you can subtract it from the initial momentum to get the final momentum. Then all you do is divide by the mass of the vehicle to get the velocity.