Without knowing Mass, how can you solve this question?

Question

During a shuffleboard game (horizontal surface) a disk is given an initial speed of 6.80 m/s. the coefficient of kinetic friction between the disk and surface is 0.290. How much time passes before the disk comes to rest?

- I suspect you start with the equation Wnet = Fnet(change in X)cos(angle)=1/2MV^2 - 1/2MV^2

Answer 1

Let mass = m

Force = coeff. of frict. * normal force = 0.29*m*g = 0.29 * 9.8 * m =  2.842*m

F=ma => a=F/m (Newton's second law). Hence acceleration = (2.842*m)/m = 0.29m/s^2, but we'll make it -0.29 since it's a deceleration.

Using the equation of motion v=u+at, making t subject gives (v-u)/a = t

Final velocity "v" is zero

Initial velocity "u" is 6.80

Acceleration "a" is -0.29 (from the above)

Therefore t = (0-6.80)/(-0.29) = 23.44 seconds

Answer 2

a = µ*g  (Imf above forgot the g)

t = dV/a = dV/(µ*g) = 6.8/(.29*9.8) = 2.39 sec