tenision in a string

Question

two blocks of equal mass m are tied to each other through a light string. One of the blocks is pulled along the line joining them with a constant force F. The tension in the string joining the blocks

Answer 1

There are a number of ways to solve this one.  Take a look at the Hyperphysics web site to see some details.

 

The easiest way is to note that the force will accelerate both blocks equally with some value, a, of the acceleration.  Newton's second law (for the system of the two blocks) is  F = (2m) a.   The 2 is there because the system mass is m + m = 2m.  So  a = F/(2m).   Now take a look at the rear block by itself.  The only force acting on it is the tension, T, in the cord.  The acceleration of this block  was determined to be a = F/(2m).   Applying Newton's second law to this block by itself gives:   T = m a = m F/(2m) =  F/2.