Two blocks, joined by a string, have masses of 6.0 and 9.0 kg. They rest on a frictionless horizontal surface. A 2nd string, attached only to the 9 kg block, has horizontal force = 30 Newtons applies to it. Both blocks accelerate. Find the tension (Force) in the string between the blocks.

Hi there!

We can begin by calculating the acceleration of the system:

∑F = ma

m = sum of the mass of both blocks

Solve for acceleration:

∑F/m = a

30/(6 + 9) = 2 m/s²

On the 6 kg block, the tension is equivalent to the net force:

∑F = T

Since we know that the 6kg is accelerating at 2 m/s², we can solve for tension:

∑F = T = ma

T = 6 · 2 = 12 N