What speed would such a block have if pushed horizontally 108 m along a frictionless track by such a laser

Hello. This question is incomplete. The full question is:

You've recently read about a chemical laser that generates a 20-cm-diameter, 25.0 MW laser beam. One day, after physics class, you start to wonder if you could use the radiation pressure from this laser beam to launch small payloads into orbit. To see if this might be feasible, you do a quick calculation of the acceleration of a 20-cm-diameter,  100 kg,perfectly absorbing block. What speed would such a block have if pushed horizontally 108 m along a frictionless track by such a laser?

V = 0.408 m / s

Explanation:

First, it is necessary to find the radiation pressure on the surface. You will find it using the following formula:

P = P / (πr ^ 2) c

where P is the pressure and c is the speed of light in vacuum

P = 25 * 10 ^ 6 / π (0.2 / 2) ^ 2 * (3 * 10 ^ 8) = 2,652 N / m ^ 2.

Then you must calculate the force (F) and the acceleration (a). This is done through the formulas:

F = P * (πr ^ 2)

F = 2,652 * π * (0.2 / 2) ^ 2 = 0.083N

a = F / m

a = 0.083 / 100 =  0.0002129 m / s ^ 2

You can now calculate the speed.

V = √2ad

V = √2 *0.0002129 * 108

V = 0.2144  m / s

For those of you taking it on Edge, the answer is C.