A certain capacitor connected in series with a resistor is being charged. At the end of 2.0 x 10-3 s its charge is 1/2 of the maximum value. What is the approximate value of the time constant of the RC circuit

Asolid cylinder and a cylindrical shell have the same mass, same radius, and turn on frictionless, horizontal axles. the cylindrical shell has light-weight spokes connecting the shell to the axle. a rope is wrapped around each cylinder and tied to blocks of equal masses that are held the same height above the ground. both blocks are released simultaneously. the ropes do not slip. which block hits the ground first? or is it a tie?