physics
posted by bill on .
You are trying to slide a refrigerator across a horizontal floor. The mass of the refrigerator is 199 kg, and you need to exert a force of 343 N to make it just begin to move.
(a) What is the coefficient of static friction between the floor and the refrigerator?
F=(mu)m*g
343\1950.2= mu
mu=.17 BUT ITS WRONG!
WHAT AM I DOING?
(b) After it starts moving, the refrigerator reaches a speed of 1.9 m/s after 4.5 s. What is the coefficient of kinetic friction between the refrigerator and the floor?
v = u + at
u =0
1.9 = 4.5 x a
a = 0.422 m/s^2
AND THATS WRONG???????????????????

I get .1758, to three significant digits. .176
On the second: find a
a= (1.90)/4.5 m/s^2=.42 m/s^2
Now, netforce= friction+ma
friction=netforcema
mu*mg=343N199*.422
solve for mu.