physics
posted by ellimac .
a 1.4 kg block slides across a rough surface such that it slows down with an acceleration of 1.25 m/s2. What is the coefficient of kinetic frisction between the block and the surface?

I assume that the surface is horizontal. The deceleration rate is F/M. So, the friction force is
a = 1.4/1.25 = 1.2 Newtons
The coefficient of sliding friction is muk = F/(M*g) = 1.2/(1.4*9.8) = ? 
Given: m= 1.4 kg
A= 1.25 m/s2
µk=Kinetic force/ Normal Force
Normal Force= 1.4*9.81(gravity) = 13.72 N
Kinetic force = net force
net force = ma = 1.4(1.25) = 1.75
µk= 1.75/13.72 = 0.13