still need a little more help... (Forces)

The static friction between the two blocks is
0.57 and kinetic friction between the block
with mass 1.8 kg and the horizontal surface is
0.14 .
The acceleration of gravity is 9.8 m/s²

What is the minimum force F which must
be exerted on the 1.8 kg block in order that
the 0.4 kg block does not to fall?
Answer in units of N

Question

still need a little more help... (Forces)

The static friction between the two blocks is
0.57 and kinetic friction between the block
with mass 1.8 kg and the horizontal surface is
0.14 .
The acceleration of gravity is 9.8 m/s²

What is the minimum force F which must
be exerted on the 1.8 kg block in order that
the 0.4 kg block does not to fall?
Answer in units of N

geerky42 · Answer

heres the figure:|dw:1349652256078:dw|

i set an equation for bigger block and I got $$\Huge{ \Sigma F_{x_1} = F_a - N_2 - f_k = ma}$$

is it right?

geerky42 · Answer

it seems that there is not enough information since i dont know Fa and a.

geerky42 · Answer

somebody help me please.

anonymous · Answer

|dw:1349657987635:dw|