Strong forces

1) are forces holding nucleons together
2) are independent of electric charge
3) act only over a very short distance
4) all of these

because growing process had stoped after 4-5 year

the moving of the box is a result of centripetal force. think of that  as a car or a truck in this case creates a turn, the force of friction performing upon the turned wheels of the car runs centripetal force obligatory for circular motion for the things inside it.