Physics problem

The charge is subject to a linear drag force βˆ’π‘v.
(a) Find the velocity of the particle, v(𝑑), if its initial velocity is v0;
(b) Find the time dependence of the kinetic energy of the particle, 𝐸(𝑑) = π‘š[𝑣(𝑑)]2/2.
Partial answer: 𝑦τ°(𝑑) = π‘’βˆ’π‘‘/𝜏 (𝑦τ°0 cos(πœ”π‘‘) βˆ’ π‘₯τ°0 sin(πœ”π‘‘)), where 𝜏 = π‘š/𝑏 and πœ” = π‘žπ΅/π‘š.