When brakes are applied to a bus the retardation produced is 25 cm square and the bus takes 20s to stop calculate the initial velocity?

When brakes are applied to a bus, retardation produced is 25 cm s-2 and the bus takes 20 s to stop.

Calculate

(i) The initial velocity of the bus

(ii) The distance travelled by the bus during this time.

Final velocity v = 0

Acceleration = -25 cm/s2 or -0.25 m/s2

Time taken t = 20 s

(i) Let 'u' be the initial velocity.

Using the first equation of motion,

v = u + at

We get,

u = v - at

u = 0 - (-0.25)(20) = 5 m/s-1

(ii) Let 's' be the distance travelled.

Using the third equation of motion,

v2 - u2 = 2as

We get,

(0) 2 - (5)2 = 2 (-0.25) (s)

s = (25/0.5) = 50 m.

Concept: Distance and Displacement

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