An electric train of mass m m\,m starts from rest and is accelerated along a straight horizontal track by an engine delivering a constant useful power PPP. Air resistance and friction are negligible.
Which of the following expressions correctly represents the velocity v v\,v of the train as a function of the distance s s\,s traveled from its starting point?
v=(2Psm)1/2v = \left(\frac{2Ps}{m}\right)^{1/2}v=(m2Ps)1/2
v=(2Psm)1/3v = \left(\frac{2Ps}{m}\right)^{1/3}v=(m2Ps)1/3
v=(3Psm)1/3v = \left(\frac{3Ps}{m}\right)^{1/3}v=(m3Ps)1/3
v=(4Psm)1/3v = \left(\frac{4Ps}{m}\right)^{1/3}v=(m4Ps)1/3
