A 2000 kg car traveling to the east is slowed down uniformly from an intitial velocity of 40.0 m/s by a 7000 N braking force acting opposite the car's motion. using the impulse momentum theorem, what is the car's velocity after 3.0 seconds?

1 Answer
May 25, 2018

From The impulse-momentum theorem we know that the change in momentum of an object equals the impulse applied to it.

sf vecJ = Deltasfvecp

If mass of the object is constant we have

vecsfFDeltasft = mΔsfvec v

Given force is braking force. Inserting given values we get

-7000xx3.0 = 2000xxΔsfvec v
=>Δsfvec v=-21000/2000=-10.5\ ms^-1

Now

Δsfvec v=sfvec v_"final"-sfvec v_"initial"
=>-10.5=sfvec v_"final"-40
=>sfvec v_"final"=40-10.5=29.5\ ms^-1