A washer weighing m = 0.1 kg slides on the ice of a frozen lake. In this case, the speed of the washer

A washer weighing m = 0.1 kg slides on the ice of a frozen lake. In this case, the speed of the washer over time t changes in SI according to the law: v = 20 – 3t. Determine what is the coefficient of sliding friction of the washer on the ice.

Consider the equation for changing the speed, its form should be reduced to the standard equation:
V = V0-a * t.
Then, comparing, we get:
a = 3, V0 = 20m / s
From the condition:
m = 0.1kg
then
Ftr = m * a
Ftr = mu * m * g
mu * m * g = m * a
mu = a / g = 3/10 = 0.3
Answer: mu = 0.3