Question

A horizontal force of 600N pulls two masses 10kg and 20kg (lying on a frictionless table) connected by a light string. What is the tension in the string? Does the answer depend on which mass end the pull is applied?

Answer 1

Because the string is thin and inextensible, then:

The general case (instead of mass 10kg and 20kg →m₁ and m₂, F= 600) Newton's second law for the mass m₁:

Answer 2

 If the 20 kg mass is pulled, 

600 - T = 20a, T = 10a 

a = 20ms^-2,  T = 200N 

If the 10kg mass is pulled, a = 20ms^-2, 

T = 400N