Question

A bus that is travelling at the rate of 90 km/h slow down to 54km/h over a distance of 20m.
S. minutes Calculate
20 m. Culate the acceleration produced and the time for which the brakes are applied​

Answer 1

Answer:

Acceleration=-10 m/s^2

(Retardation =10 m/s^2)

Time for which brakes are applied=1 second

Step-by-step explanation:

Firstly,the answer should always be in SI units so convert initial and final velocity into m/s

u= 90 km/hr=90×5/18 =25 m/s

v= 54 km/hr=54×5/18 = 15 m/s

Then apply the third equation of motion

v^2= u^2+2as

(15)^2=(25)^2+2×a×20

225=625+40 a

225-625=40 a

a-400/40=-10 m/s^2

To calculate time use first equation of motion

v=u+ at

15 =25+( -10 ×t)

15-25=-10 t

t=-10/-10 = 1 second.

Answer 2

Answer:

Step-by-step explanation:

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