Question

A bus was moving with a speed of 54km/h. On applying brakes , it stopped in 8 seconds . Calculate the acceleration and the distance travelled before stopping.​

Answer 1

Answer:

60m and -1.875m/s^2

Step-by-step explanation:

Given:-

The bus had an initial velocity of 54 km/h.

On applying brakes, the bus took a time of 8 secs to stop.

To calculate:-

The acceleration of the bus before stopping.

Solution:-

Initial velocity of the bus (u) = 54 km/h = 54/3.6 m/s = 15 m/s

Final velocity of the bus (v) = 0 km/h = 0 m/s   (∵As the bus finally stops)

Using Newton's first law of motion,

v = u + at

⇒0 = 15 + 8a

⇒ -15 = 8a

⇒a = -15/8

⇒

As the sign is negative, so a deceleration has occurred.

Using Newton's second law of motion,

s = ut + 1/2 at²

⇒s = 15*8 + 1/2*-1.875*(8)²

⇒s = 120 + 1/2*-120

⇒s = 120 + (-60)

⇒s = 120 - 60

⇒

∴So, the acceleration and the distance of the bus before stopping are -1.875 m/s² and 60 m respectively.