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?

Answer 1

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) = ?

Answer 2

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