Your question has been heard loud and clear.
a)
Initial velocity , U=50km/h = 250/18 m/s
Final velocity , V = 0 (this is because the car finally comes to rest)
From 3rd equation of motion , V^2-U^2=2AS.
Now , for a car that goes 50km/h , it has been proven that miniumum brake distance is 6 metres.
so , S = 6 metres.
Using this , we can find the distance stopped by car , and then we can find time.
0-(250/18)^2=2*A*6
0= 2*A*6+(250/18)^2
0 = -12A + 192.90 ( minus sign because car is deccelerating)
So , A = 16.07 m/s^2
V^2-U^2 = 2AS
0 - 192.90 = 2* 16.07*S
So , S (distance) = 24 metres.
Now , we know time = distance / speed
so , time = 24 / 253 = 0.094 seconds
Thank you
