posted by Connie .
A sled is pushed by 12 monkeys with a constant force until it reaches a velocity of 18.9 m/s. All 12 monkeys stop pushing and the sled slides across a rough surface. From the time the monkeys stop pushing the box slides 12.3 meters before it comes to a stop. If the u of k of the contact is 0.21, what is the mass of the sled?