can't figure this out?

Question

In the 1950's, an experimental train that had a mass of 15,400 kg was powered across a level track by a jet engine that produced a thrust of 568,000 N for a distance of 459 m. What's the change in kinetic energy (J)? What's the final kinetic energy if the train started from rest (J)? What's the final speed of the train assuming no friction (m/s)?

Answer 1

well, this is pretty easy. work = force*change in position
in this case work = 568,000N * 459m = 260,712,000 J.
This is the answer for the first two parts.

since the kinetic energy = 260,712,000 = 1/2*mass*velocity^2 we get that mass*velocity^2 = 521,424,000
velocity^2 = 33,858.7013
velocity = ~184 m/s

Answer 2

F*S = 0.5 m V V.

F*S = 568,000 x 459 = 2.6 x 10^8 J.

This is the change in kinetic energy.

If the initial kinetic energy is zero then final kinetic energy = cahnge in kinetic energy =2.6 x 10^8 J.

0.5 m v*v = 2.6 x 10^8 J.============= m =15,400

v = 184 m/s.

Answer 3

ke = 1/2 mv^2
where m is the mass (15400) and v is the final speed.

We know f = ma, so the acceleration is 568000/15400, or 3.68 m/s^2

to compute the final velocity, use v^2 = vi^2 + 2as where vi^2 is the initial speed, and s is the distance, so
v^2 = 0 + 2*56800/15400*459 = 3385

So, plugging v^2 into the formula for kinetic energy, we get
ke = 1/2*15400*3385
or 2.6 times 10^7 kg m^2/s^2