A race dog is initially running at 10 m/s but is slowing down. How fast is the dog moving when its kinetic energy has been reduced by half? A boulder with a mass of about 1.5 x10^5 kg falls and strikes the ground at 70 m/s. How much kinetic energy does the boulder deliver to the ground? in joules

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?