007.3 Forces Add
Suppose a one kilogram object is accelerating upwards at one meter per second per second.
The total force on the object must be one Newton upwards. Since that total is the result of a downward force of 9.8N due to gravity and an upward force on the chain, the force on the chain must be 10.8N so that when the forces are added, taking direction into account,
| 10.8N - 9.8N = 1N |
Two one-kilogram objects, each accelerating side-by-side at one meter per second per second will each feel a total force of one Newton. The total force on the pair is then two Newtons.
Tieing the two objects together should make no difference, so a force of 2N on a pair of one kilogram objects will cause them to accelerate at one meter per second per second.
Examples like this suggest that the total force F, the mass m, and the acceleration a are related by the formula a = F/m.