Question

1. A train moving at 36km/hr reduces it's speed to 4m/s in 15 minutes. Calculate the acceleration.

2. calculate the initial velocity when a speed of train is reduced to 7m/s after 28 seconds.The retardation due to brakes is 0.5m/s².
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Answer 1

Answer:

(1) -1/150 m/s^2

(2)21m/s

Explanation:

well it's very easy question

first of all write all the measures given:-

for 1st case:-

u=36km per hour

first convert this speed in m/s

for this convertion let 36 multipled by5/18= 10 m/s

now, v=4m/s

time=15 mins or 15 into 60 second=900seconds (always remember to first convert the units in thie SI unit ) VERY IMPORTANT!!!

Now,we know that

a=v-u/t

a=4-10/900= -6/900 =-1/150 m/s²

(2) part

write all the things given:-

u to be calculated=?

v=7m/s

t=28 seconds

a=-0.5m/s²(remember since it is retardation take the acceleration negative)

a=v-u/t

-0.5=7-u/28

-14=7-u

u=(14+7)m/s or 21 m/s

Thanks for giving me the previlidge to help you.!!