What is the magnitude of the force exerted on the block with mass 8kg by the block with mass 6kg?

Question

F(l)_____________F(r)
---->|2kg| |8kg| |6kg|<---
F(l) is the force on the left and is 12 N
F(r) is the force on the right and is 8N

Answer 1

Start by figuring out the acceleration of all the blocks together.
Fnet = ma
a = Fnet/m =( F(l) - F(r) )/m
a = (12 - 8)/16 = 1/4 m/s^2 to the right

Each individual block will have this same acceleration.
Lets just examine the 6kg block. (using F(8) to represent the force from the 8kg block)

Fnet = F(8) - F(r) = m a
F(8) = m a + F(r)
F(8) = 6* 1/4 + 8 = 19/2 N

By Newton's Third law the force from the 6kg block on the 8kg block is the same as the force from the 8kg block on the 6kg block but in the opposite direction.

So the answer is 19/2 N to the left.