1.) In the 1950s, an experimental train that had a mass of 2.50x10^4kg was powered across a level track by a jet engine that produced a thrust of 5.00x10^5 N for a distance of 509m.(adsbygoogle = window.adsbygoogle || []).push({});

A-Find the work done on the train.

B-Find the change in Kinetic Energy.

C-Find the final kinetic energy of the train if it started from rest.

D-Find the final speed of the train if there were no friction.

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A...W=Fd....W=(5.00e^5N)(509m)....W=2.5e^8.

B,C, and D I cannot understand. For part b, I believe you use KE=1/2mv^2, but I have no velocity..., if I had a quantity for velocity, I would be able to find ΔKE by doing K1=...,K2=.... and finally...W=K2-K1=.....J.

For c and d, I'm totally lost.

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2.) A 14,700N car is traveling at 25m/s. The brakes are applied suddenly, and the car slides to a stop. The average braking force between the tires and the road is 7100N.How far will the car slide once the brakes are applied?

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Well, I know this:

F=14,700 N

Vi=25 m/s

Vf=0 m/s

avg. braking force=7100 N

and I'm assuming that I need to find d=......?

What formulae would I use to find the answer? I know these:

KE=1/2mv^2

W=ΔKE

W=fd. I'd be able to solve for d, but how would I go about finding the value for W?

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# Homework Help: Two energy problems I do not understand

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