I have been annoyed by a problem that I can't figure out. The topic is work and kinetic energy (chapter 6 in the sixth edition of(adsbygoogle = window.adsbygoogle || []).push({}); physics for scientist and engineersby Paul A. Tipler). Problem 63 pg. 199

A single horizontal force F acts in the +x direction on a mass m. The intial velocity is zero, the velocity is given as a function of x v=Cx where C is a contant. If the starting point x=0 and the final point is x = x' find the force and the work.

my solution is w= .5mv^2 = .5m(Cx')^2 Therefore Fx' = .5m(Cx')^2 therefore

F=.5mx'C^2 which is the correct answer.

However, first I tried to do this

f=ma = m (dv/dt) = m[C*dx/dt] = mCx' Why is this wrong???

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Work/kinetic energy problem

**Physics Forums | Science Articles, Homework Help, Discussion**