Question

if a bus travelling at 20 m/s is subjected to a steady deceleration of 5 m/s2,how long will it take to come to the rest ?

Answer 1

For the bus,

Initial Velocity, u = 20 m/s
Final Velocity, v = 0 m/s
Acceleration, a = -5m/s²  (minus sign because of deceleration)
Time, t = (?)

We know that,

a = (v - u)/t
∴t = (v - u)/a
∴t = (0 - 20)/(-5)
∴t = (-20)/(-5)
∴t = 4s

Thus, the bus will take 4 seconds to stop.

Answer 2

The time taken by the bus to come to rest is 4 seconds.

Given,

The velocity of the bus = 20 m/s

The bus is subjected to a steady deceleration of 5 m/s.

To Find,

The time taken by the bus to come to rest.

Solution,

Using the equation of motion

v = u + at

where,

v = final velocity = 0 m/s

u = initial velocity = 20 m/s

a = acceleration = -5 m/s²

t = time taken

So,

0 = 20-5(t)

5t = 20

t = 20/5 = 4

t = 4 seconds.

Hence, the time taken by the bus to come to rest is 4 seconds.

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