What is the maximum mass of a rubber block that can be pulled by a rope whose maximum tension is 3500N? The block is sitting on dry asphalt.
(By the way, 1.2 would be used as the coefficient of static friction and 0.8 is the coefficient of kinetic friction for rubber substance on dry asphalt)
As the rope will break when T > 3500 N (we presume) that's the maximum resistance force that can be pulled. But, this is important, that force F = k W comes from a combination of the coefficient of sliding friction, k, and the weight W of the rubber block, whose mass is m = W/g.
So there you are. If k = .1, then F = T = 3500 = k W = .1 W and W = 35000 N so the mass is m = W/g ~ 35000/10 = 3500 kg.
But if k = .5, the F = T = 3500 N = k W = .5 W so that W = 7000 and m = W/g = 7000/10 = 700 kg. Considerably less mass when the coefficient is higher.
I hope this helps!