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A freight train has a mass of 15000000 kg. If the locomotive can exert a constant pull (what is a constant pull?) of 750000 N, how long would it take to increase the speed of the train from rest to 85 km/h? (Disregard friction.)

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- #1

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A freight train has a mass of 15000000 kg. If the locomotive can exert a constant pull (what is a constant pull?) of 750000 N, how long would it take to increase the speed of the train from rest to 85 km/h? (Disregard friction.)

- #2

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newtons second law: f=ma, a=f/m. You can use this to derive the acceration and use some kinematics formulas to find out how long it will take to reach a certain velocity with a known acceleration and a known initial velocity.

Last edited:

- #3

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F = ma

750000 N = (15000000 kg) * a

750000 N = (15000000 kg) * a

- #4

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You can easily find this acceleration by using the values already given.

You now can use this in a kinematics equation. You have acceleration,initial velocity,final velocity, and you need to find time.

I suggest using this equation:

V(f)=V(i)+at

By the way, make sure you watch your units. The final velocity that the problem gives is in kilometers per hour. Convert this speed to standard units.

Hope this helps

- #5

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- #6

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conversion from m/s to km/h

- #7

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They are looking for time in this problem.

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