A 5.0 kg moving at an initial speed of 6.0 m/s slides 20 m to the right on a horizontal floor before it comes to a complete stop. What is the force of friction?

Answer 1

6t + 1/2 at^2 = 20
6 + at = 0

at = -6, so
6t - 1/2 * 6t = 20
t = 20/3

a = -9/10
F = ma