B. Total momentum should be mass x velocity, or 1600 x 25 = 40000 Kg m/s

C. To find the the time the car will stop, we can use the kinematics formula that has initial speed, final speed, acceleration and time in the equation.

ie we can use Vfinal = Vinitial + acceleration x time

Vfinal = 0 m/s because we bring it to a full stop

Acceleration can be found from the Force equation F=mass x acceleration so acceleration = F/mass. And since the direction the mass is travelling in and the force acting upon it goes opposite direction, we can put a negative sign in the Force (-650 N)

So 0 = 25 + (-650/1600) x t

t = 25/(650/1600) = 61,53845 sec

2. impulse can be found by calculating change in momentum, so we can use the equation:

m x Vfinal – m x Vinitial = impulse

of course you will need to convert the speed to m/s so this becomes 90 x 1000/3600 m/s = 25 m/s

now see that the m does not change and so we can simplify the equation to become

impulse = m (Vfinal-Vinitial)

= 2000 (0-25)

= -50000 kg m/s