If a 2 kg ball traveling at 10 m/s hits a wall and stops in 0.03 seconds, then how much force will the ball experience?

Newton's second law is:

F=m*a,

where a=dv/dt, so

F=m * (dv/dt)

Rearranging gives:

F*dt=m*dv.

Basic integration gives:

F*t=m (vf-v0),

where vf and v0 are the final and initial velocities of the object respectively.

In your case vf=0, because the ball stops completely, and v0=10m/s.

Rearranging the last expression gives F = (m (vf-vo)) / t.

Plug in numbers to find F = (2*10) / 0.03=666.6 N