Part A If the engineer disengages the engine, how much time will it take the loc

Question

Part A

If the engineer disengages the engine, how much time will it take the locomotive to coast to a stop?

Express your answer using two significant figures.

Part B

How far will the locomotive move during this time?

Express your answer to two significant figures and include the appropriate units.

The rolling resistance for steel on steel is quite low; the coefficient of rolling friction is typically ? r =0.002 m/s on level rails. Part A If the engineer disengages the engine, how much time will it take the locomotive to coast to a stop? Express your answer using two significant figures. Part B How far will the locomotive move during this time? Express your answer to two significant figures and include the appropriate units. kg locomotive is rolling at 25 m/s Mux = 0.002 . Suppose a 180,000 kg

Explanation / Answer

Part A)

The force to stop it is F = uFn

F = (.002)(180000)(9.8)

F 3528 N

Then F = ma

3528 = (180000)(a)

a = .0196 m/s2 (We need to use this as a negative since it is slowing the train)

Then apply vf = vo + at

0 = 25 + (-.0196)t

t = 1276 sec

Round to 1300 sec using two sig figs...

Part B)

Apply vf2 = vo2 + 2ad

0 = 252 + 2(-.0196)(d)

d = 15944 m

Round to 16000 m using two sig figs (1.6 X 104 m)

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