What is the purpose of using the string to tie the forelegs and hind legs during dissection?

A10.0 kg cart and a 15kg cart are locked together with a compressed spring between them. they are then released so that the spring pushes the two carts apart. the 10.0 kg cart is moving at 4.5 m/s afterward. how fast is the 15kg cart moving? 3.0 m/s 2.0 m/s 4.5 m/s 5.0 m/s

Idon’t quite understand this problem

Sound is a disturbance that travels through a medium as a