Ap physics, needed all work steps and list all the variables, value and units

Question

A 15,680 N car, initially traveling at 20 m/s, applies a braking force of 640 N. The car comes to a complete stop.  

1. Determine the car’s mass in [kg].
2. Determine the car’s initial momentum in [kg m/s]
3. Calculate the car’s change in momentum in [kg m/s]
4. Calculate the time, in [s], it takes the braking force to bring the car to a complete stop

Answer 1

Note for AP I highly recommend using g=10 as a lot of conceptual questions from the college board use 10. This question however does use 9.8

1) Weight = mg therefore mass = 15680/9.8 = 1600 kg

2) Momentum p = mv = (1600)(20) = 32,000 kg m/s

3) If it comes to a complete stop the change in momentum is mΔv = 1600 (-20) = -32,000 kg m/s

4) Using the impulse equation FΔt = mΔv we get Δt = -32,000/640 = 50 seconds