Calculate the acceleration of the system

AI Thread Summary
To calculate the acceleration of the system with two crates, a 620 N force is applied to the 60 kg crate, while the kinetic friction coefficient is 0.15. The frictional force opposing the applied force is calculated using the mass of both crates and the gravitational acceleration, leading to a net force that determines the system's acceleration. The initial attempt incorrectly used the friction force as acceleration, which is not accurate. The correct approach involves calculating the net force after accounting for friction and then applying Newton's second law to find the acceleration. Understanding the role of friction is crucial for accurate calculations in this scenario.
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Two crates, of mass m1 = 60 kg and m2 = 130 kg, are in contact and at rest on a horizontal surface (Fig. 4-54). A 620 N force is exerted on the 60 kg crate. The coefficient of kinetic friction is 0.15.

(a) Calculate the acceleration of the system.
m/s2 (to the right)
(b) Calculate the force that each crate exerts on the other.
N
(c) Repeat with the crates reversed. acceleration m/s2
crate force N


I'm trying to caculate the acceleration and I can't seem to get it. I tried this but I know it is incorrect:

Mk*G=a

.15 * (60*9.8) - .15 *(130*9.8)= -102.9

Can someone tell me where I'm going astray?
 
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<br /> \mu_{k} mg<br />
is not your acceleration. It is the force exerted by kinetic friction. It opposes the 620 N force applied to the 60 kg crate.
 

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