Asmall block of mass m slides on a horizontal frictionless surface as it travels around the inside of a hoop of radius r. the coefficient of friction between the block and the wall is mu; therefore, the speed v of the block decreases. in terms of m, r. mu, and v, find expressions for each of the following. b. the block's tangential acceleration dv/dt c. the time required to reduce the speed of the block from an initial value v0 to vo/3