Posted by **PLZ HELP ME NOW...** on Wednesday, May 30, 2012 at 6:03am.

a train starts from rest and accelerates uniformly at 100m/min^2 for 10 min.then it maintains a constant velocity for remaining 20 min.brakes are applied and train uniformly retards and comes to rest in next 5 min.

a)the maximum velocity reached

b)the retardation in last 5 min

c)total distance traveled

d)the average velocity of the train.

- physics -
**Elena**, Wednesday, May 30, 2012 at 12:39pm
v=a•t1 =100•10 = 1000 m/min.

s1 = a1•t1²/2 =100•100/2 =5000 m.

s2=v•t2 =1000•20 =20000 m.

0 =v +a2•t3,

a2 = -v/t3 = - 1000/5 = - 200 m/min,

s3 = v •t3 – a2•t3²/2 =1000•5 - 200•25/2 =2500 m

s = s1 + s2 +s3 = 5000 + 20000+ 2500 = 27500 m.

t =t1+t2+t3 = 10 +20 =5 = 35 min.

v(ave) =s/t = 27500/35 =785 m/min.

a) 1000 m/min,

b) - 200 m/min,

c) s = 27500 m.

d) v(ave) =785 m/min.

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