# Train force physics problem

1. Jun 16, 2010

### mandy9008

1. The problem statement, all variables and given/known data
A freight train has a mass of 1.4x107 kg. If the locomotive can exert a constant pull of 6.7x105 N, how long does it take to increase the speed of the train from rest to 84 km/h?

2. Relevant equations
F=ma
a=v/t

3. The attempt at a solution
I converted 84 km/h into 23.3 m/s.
F=ma
6.7x10^5 N=1.4x10^7 m (a)
a= .047 m/s^2

a=v/t
.047 m/s^2=(23.3 m/s)/t
t=495.7s --> 2.97x10^4 min

Last edited: Jun 16, 2010
2. Jun 16, 2010

### rock.freak667

Re: Force

That looks correct.

3. Jun 16, 2010

### mandy9008

Re: Force

when I enter it it says that it differs significantly from the correct answer

4. Jun 16, 2010

### rock.freak667

Re: Force

the t =2.97x104 min is not correct.

t= 495.7 s should be correct.

5. Jun 16, 2010

### mandy9008

Re: Force

the question asks for time in minutes

6. Jun 16, 2010

### mandy9008

Re: Force

i converted it and got 8.26 min and got it correct.i don't know what i was thinking converting it before haha thanks