How long does it take electrons to get from the car battery to the starting motor? assume the current is 143 a and the electrons travel through copper wire with cross sectional area 40.2 mm2 and length 84.5 cm . the mass density of copper is 8960 kg/m3 and the molar mass is 63.5 g/mol . avogadro’s number is 6.022 × 1023 . assume that each copper atom contributes one conduction electron.

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?