Explanation:
Mass of car = 1000 kg
Deceleration = 5 m/s²
Decelerating force = Mass x Deceleration
Decelerating force = 1000 x 5 = 5000 N
We need to find time the time taken to stop
We have equation of motion v = u + at
Initial velocity, u = 20 m/s
Final velocity, v = 0 m/s
Acceleration, a = -5 m/s²
Substituting
v = u + at
0 = 20 + -5 x t
t = 4s
Impulse = Force x Time
Impulse = 5000 x 4 = 20000 Ns
Magnitude of the impulse applied to the car to bring it to rest is 20000 Ns