I attached a Diagram for this problem.
We star considering the system is in equlibrium, so
Fm makes
with vertical
Fm makes 70 with vertical
Applying summatory in X we have,


We know that W is equal to

Substituting,




<em>For the second part we know that the reaction force Fj on deltoid Muscle is equal to Fm, We can assume also that</em> 
Answer:
v=0.60 m/s
Explanation:
Given that
m ₁= 390 kg ,u ₁= 0.5 m/s
m₂ = 250 kg ,u₂ = 0.76 m/s
As we know that if there is no any external force on the system the total linear momentum of the system will be conserve.
Pi = Pf
m ₁u ₁+m₂u₂ = (m₂ + m ₁ ) v
Now putting the values in the above equation
390 x 0.5 + 250 x 0.76 = (390 + 250 ) v

v=0.60 m/s
Therefore the velocity of the system will be 0.6 m/s.
v^2 = v0^2 +2ad
v^2 = 22^2 + 2*3.78*45 = 824.2
v= √824.2 = 28.7 m/s
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