Find d with m and v

krisrai · May 18, 2008

If a 50 000 kg locomotive is travelling at 10m/s and its brakes and engine both fail, how far will it roll before coming to a stop.

Now I know how to do this problem if friction was given but I really dont know which formulas i can combine.

I think I need to find deceleration but I dont know how with the information given.

If someone could give me a hint how to get started it would be appreciated:)

rock.freak667 · May 18, 2008

Are you sure that is all the question gave? Because if you ignore friction, then there must be some other force acting on the train, else by Newton's first law, that train should continue to move in a straight line.

warmfire540 · May 18, 2008

sorry man, there is no way to find this..because we need to find the deceleration..which is either
a. negative acceleration because of engine
b. negative acceleration because of friction

we know that it's v=10ms-1, but we don't know a time or accel

krisrai · May 18, 2008

i know, if there was friction i could use ma=mgUs and find acceleration to sub into a kinematics formula to find d skidding

the question oly gives what i wrote above

krisrai · May 18, 2008

my textbook gives the answer as 2550m

SheldonG · May 18, 2008

krisrai said: ↑

If a 50 000 kg locomotive is travelling at 10m/s and its brakes and engine both fail, how far will it roll before coming to a stop.

Now I know how to do this problem if friction was given but I really dont know which formulas i can combine.

I think I need to find deceleration but I dont know how with the information given.

If someone could give me a hint how to get started it would be appreciated:)

I think you can assume the engine is running constantly, providing a force to push the train. But the train is not accelerating, it is traveling at 10 m/s. When the engine fails, the resistive force that keeps the train traveling at 10 m/s is the only force remaining, since the brakes also fail.

Sheldon

hage567 · May 18, 2008

This problem has been presented before. Here is the thread https://www.physicsforums.com/showthread.php?t=167002. See if that helps.

krisrai · May 18, 2008

definitely helps thank you hage
I just wasnt expecting that i would have to look up the coefficient of rolling friction like pingpong did.

hage567 · May 18, 2008

Yeah, I agree that's a bit strange.

Log in or Sign up

Find d with m and v

krisrai

rock.freak667

warmfire540

krisrai

krisrai

SheldonG

hage567

krisrai

hage567

Dynamics question- finding m in terms of rho, r and v (Replies: 3)

SHM find F, with A, v, and m (Replies: 1)

Circular motion, find V when only given m and r (Replies: 3)

Calculate F given m, d, and v should be easy. (Replies: 9)

How to find the speed of an ion using V, T, m, q? (Replies: 8)