Question

ULIULIOL

THIS. AJUSI
A bus is moving with a velocity of 72 km/hr. On seeing the red signal of traffic
at 27 m ahead on the road, the driver applied brakes and the bus stopped at a
distance of 25 m. Calculate the time taken by the car to come at rest. (Ans: 2.5 s)
with
of 60 km/hr. On seeing a child at 11m ahead on
A
a​

Answer 1

The time taken by the car to come at rest is 2.5 seconds

Step-by-step explanation:

The parameters given are;

Speed of bus = 72 km/hr

Distance at which bus stopped = 25 m

Given that the speed and the distance covered before stopping are j=known, we have;

v² = u² - 2·a·s

Where:

v = Final velocity = 0

a = Deceleration of the bus

s = Distance covered while decelerating = 23 m

u = Initial velocity = 72 km/hr = 20 m/s

Which gives;

0² = (20 m/s)² - 2×a×25 m

20² = 2×a×25 m

a = 20²/(2×25) = 8 m/s²

The time, t, it takes for the car to come at rest is given by the relation;

v = u - at

0 = 20 - 8×t

t = 20/8 = 2.5 s.