Proton mass and velocity when kinetic energy is half total energy

[a.a]

Homework Statement

a) Calculate the mas of a proton ( ms = 1.67 * 10^-27 kg) whose kenetic energy is half its toral energy. (ANS. 3.34 * 10^ -27 kg)
b) How fast is it travelling? ( ANS. 0.87c) c- speed of light

Homework Equations

E(kenetic) = Gm(1)m(2) all over R^2

E(total) = -0.5Gm(1)m(2) all over R

V(orbit) = sqrt. GM/r, where M is the mass of planetary object

E = mc^2

The Attempt at a Solution

The most I can come up with is that there is no gravitational potential energy because
1/2E(k) = E(total)

 

[Hootenanny]

a) Calculate the mas of a proton ( ms = 1.67 * 10^-27 kg) whose kenetic energy is half its toral energy. (ANS. 3.34 * 10^ -27 kg)

I believe the question is asking for the proton's relativistic mass.

 

[astrorob]

http://hyperphysics.phy-astr.gsu.edu/hbase/Relativ/releng.html

This may help you.

N.B. You don't need any of those equations apart from Einstein's.