Question

A bus was moving with a speed of 54 km/h. On applying brakes it stopped in 8 seconds. Calculate the acceleration.

Answer 1

SPEED (v) = 54KM/H = 54 X 1000 / 60 X 60 = 54000/3600 = 15M/S

  TIME (t) = 8 SECS.

  DISTANCE (s) = ?

  SPEED = DISTANCE / TIME

  15   = DISTANCE/8

  15 X 8 = DISTANCE

  120 = DISTANCE.

  OR,

  DISTANCE = 120 M.

NOTE:- SPEED IS SAME AS VELOCITY IN THIS CASE.

FOR ACCELERATION,

  INITIAL VELOCITY (u) = O

  FINAL VELOCITY (v) = 15M/S

  TIME (t) = 8 SECS.

ACCELERATION (a) = v-u/t

  = 15-0/8

  =15/8

  = 1. 875 M/S2.

Answer 2

In the above Question, the following information is given -

A bus was moving at a speed of 54 km/h. On applying brakes it stopped in 8 seconds.

To find -

Calculate the acceleration of the bus.

Solution-

Here,

A bus was moving at a speed of 54 km/h.

Now,

54 km

2w

=> 54 × ( 5 / 18 ) m/s

=> 15 m / s .

Hence, the initial Velocity of the bus is 15 m / s.

The bus stops finally.

Hence, the final velocity of my bus is 0 m / s.

Time is taken for the bus to stop = 8 seconds.

So, we know the following -

u = 15 m / s

V = 0 m / s

t = 8 s

Now, according to the first equation of motion -

V = u + at

=> 0 = 15 + 8 t

=> a= - ( 15 / 8 ) m / s²

=> a = -1.875 m / s²

The negative sign indicates that this is retardation...

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