Side-by-Side Blocks with Force pushing it

[ifeelretarded]

Homework Statement

Three blocks are in contact with each other on a frictionless, horizontal surface. A horizontal force F is applied to m₁. If m₁= 2 kg, m₂= 3 kg, m₃= 4 kg, and F= 18 N, find (a) the acceleration of the blocks, (b) the resultant force on each block, and (c) the magnitude of the contact forces between the blocks.

Homework Equations

(a) F - N₁₂ = m₁a
N₂₁ - N₂₃ = m₂a
N₃₂ = m₃a

(b) R₁ = m₁a
R₂ = m₂a
R₃ = m₃a

The Attempt at a Solution

(a) I found that a= 2 m/s²

(b) R₁ = 4 N
R₂ = 6 N
R₃ = 8 N

(c) I have no idea what "the magnitude of the contact forces between the blocks" means. Can somebody please tell me if I've done (a) and (b) right? And how to do (c)?

 

[rl.bhat]

Hi ifeelretarded, welcome to PF.

Your part a is correct.
To find the contact force, find the net force acting on each block.
The net force acting on m1 is
F - F1 = m1*a, here F1 is the contact force between m1 and m2.
Similarity you can find tha contact force between m2 and m3.

 

[rl.bhat]

Hi ifeelretarded, welcome to PF.

Your part a is correct.
To find the contact force, find the net force acting on each block.
The net force acting on m1 is
F - F1 = m1*a, here F1 is the contact force between m1 and m2.
Similarity you can find tha contact force between m2 and m3.

 

[ifeelretarded]

Hi ifeelretarded, welcome to PF.

Your part a is correct.
To find the contact force, find the net force acting on each block.
The net force acting on m1 is
F - F1 = m1*a, here F1 is the contact force between m1 and m2.
Similarity you can find tha contact force between m2 and m3.

So F1 was already previously found in part (b)?

 

[rl.bhat]

No. R1 is the net force
R1 = 18N - F1.
Find F1.