Modern Physics (S. Theory of relativity) problem

[majormuss]

Homework Statement

Find the force necessary to give a proton an acceleration of 1.0 10e19 m/s2 when the proton has the following velocities (along the same direction as the force).

Homework Equations

P=mλu

The Attempt at a Solution

Found the derivative of the above equation and got F=mλa, but my answers are been rejected by the school software. I don't know what I did wrong please help.

 

[TSny]

The gamma factor λ depends on u. Since p is proportional to the product of λ and u, you'll need to use the product rule when taking the derivative dp/du in the expression F = dp/dt = (dp/du)(du/dt)