A tradesman sharpens a knife by pushing it against the rim of a grindstone. The 45 cmcm diameter stone is spinning at 200 rpmrpm and has a mass of 25 kgkg . The coefficient of kinetic friction between the knife and the stone is 0.20.
If the stone loses 10% of its speed in 10 ss of grinding, what is the force with which the man presses the knife against the stone?
N = ?
