What are the forces acting on the 2 kg mass?

[mandy9008]

Homework Statement

Assume the three blocks portrayed in the figure below move on a frictionless surface and a force F = 40-N acts as shown on the m = 3.0-kg block.

(a) Determine the acceleration given this system.
(b) Determine the tension in the cord connecting the 3.0-kg and the 1.0-kg blocks.
(c) Determine the force exerted by the 1.0-kg block on the 2.0-kg block.

Homework Equations

F=ma

The Attempt at a Solution

a. F=ma
40N = (1kg + 2 kg + 3kg)a
a=6.67 m/s²

b. T=m(a+g)
T= 6kg (6.67 m/s² + 9.8 m/s²)
T=99N
OR (I tried both)
T=4kg (6.67 m/s² + 9.8 m/s²)
T=66N

c. F=ma
F= 3kg(6.7 m/s²)
F=20.1 N
foc

 

[Doc Al]

The Attempt at a Solution

a. F=ma
40N = (1kg + 2 kg + 3kg)a
a=6.67 m/s²

Good.

b. T=m(a+g)
T= 6kg (6.67 m/s² + 9.8 m/s²)
T=99N
OR (I tried both)
T=4kg (6.67 m/s² + 9.8 m/s²)
T=66N

Not sure where you are getting g from in your equations. The only forces we care about here are horizontal.

Hint: Analyze the forces acting on the 3 kg mass.

c. F=ma
F= 3kg(6.7 m/s²)
F=20.1 N

Why 3 kg? Hint: Analyze the forces acting on the 2 kg mass.