Question

a train is moving with a velocity of 90 km per hour. It is brought to stop by applying the brakes which produce a retardation of 0.5 m per s square find the velocity after 10 s and the time taken by the train to come to rest

Answer 1

a) u=90km/h=90000/3600=25 m/s
t=10 s
a=-0.5 m/s2
v=u+at=25+(-0.5)(10)
=25+(-5)=20 m/s
b)u=25 m/s
v=0
a=0.5 m/s2
v=u+at
0=25+(-0.5)t
-25=-0.5t
t=25/0.5
=25×10/5=50 s
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Answer 2

Answer:

i) v = 0

a = - 0.5 m/s²

t = ?

u = 90 × 5/18 m/s = 25 m/s

v = u + at

0 = 25 + (- 0.5) t

0= 25 - 0.5t

0.5 t = 25

t = 25 / 0.5

t = 50 s

ii) u = 90 km/h = 90 × 5/18= 25 m/s

a = - 0.5 m /s²

t = 10 s

v = u + at

v = 25 + ( - 0.5) 10

v = 25 - 5 = 20 m/s

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