Answer:
m1=914.9kg
m2=604.9kg
m3=864.75kg
Step-by-step explanation
I think we are suppose to find the mass of the crate.
The effective force that moves the body in positive x direction is 3615N
ΣFx = Σma
Then Fx=3615N
Then the masses be m1, m2 and m3
Then,
ΣF = Σ(ma)
3615=(m1+m2+m3)a
Given that a=1.516
The masses are
m1+m2+m3=, 2384.56. Equation 1
Between mass 1 and mass 2 is, F12=1387.
The effective force that pull mass 1 is 1387.
F12=m1 ×a
Therefore,
m1=F12/a
m1=1387/1.516
m1=914.9kg.
The effective force that pulls crate 1 and crate 2 is F23
F23=(m1+m2)a
Therefore
2304=(m1+m2)a
Therefore, since a=1.516
m1+m2=2304/1.516
m1+m2=1519.8kg
Since m1=914.9kg
So, m2=1519.8-m1
m2=1519.8-914.9
m2=604.9kg
Also from equation 1
m1+m2+m3=2384.56
Since m1=914.9kg and m2=604.9kg
Then, m3=2384.56-604.9-914.9
m3=864.75kg