Homework Help: physics!

Posted by monica on Wednesday, January 5, 2011 at 6:43pm.

A freight train has a mass of 1.8 × 10
7
kg.
If the locomotive can exert a constant pull
of 6.2×10
5
N, how long does it take to increase
the speed of the train from rest to 70 km/h?
Answer in units of min.

physics! - Damon, Wednesday, January 5, 2011 at 6:48pm
F = m a
6.2 * 10^5 = 1.8 * 10^7 a

a = (6.2/1.8)10^-2 m/s^2

v = a t

now what is v
70,000 m/3600 s = 19.4 m/s
so
t = (19.4 * 1.8 /6.2 )* 10^2 seconds

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