Calculating Acceleration in an Inclined Force Problem with Pulley Setup

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The discussion revolves around calculating the acceleration of a two-mass system involving a pulley, where M1 is 5 kg on an incline and M2 is 4 kg hanging vertically, with a friction coefficient of 0.20 and an incline angle of 40 degrees. The teacher indicated the correct acceleration is 0.02 m/s², but the student consistently calculated 3.5 m/s². The student used equations involving tension and friction but failed to account for all forces acting on M1 down the slope. Clarification is sought on the correct approach to solve the problem, emphasizing the need to consider all forces involved. Understanding the complete force dynamics is crucial for arriving at the correct acceleration value.
jinjin11
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I am having trouble on one of my homework problems. The problem is

What is the acceleration of the system if M1 is 5 kg and M2 is 4kg and the coefficient of friction between M1 and the table is 0.20? There is an image along with the problem. Basically it is just like a standard inclined plane problem where M1 is the box on the ramp and M2 is the weight being pulled down. The angle of incline is 40degrees.

The teacher stated that the answer was 0.02m/s2, but that we would have to show all work to receive credit. I have worked it out several times, but have not been able to get that answer. He taught is to do this by plugging values into the equations T−mg=ma and T−Ff=ma, setting the tensions equal to each other, and finding the acceleration. I did this, but got something along the lines of 3.5m/s2. I looked up alternative methods online, but they didn't seem to use the second equation, and I was a little confused. If someone would teach me the steps to solve this problem, I would very much appreciate it.

The specific work I did was the following:
T = mg + ma
T = 4(9.8)+4(-a)
T = friction + ma
T = 0.2(38) + 5a
Set equations equal to each other.
39.2 - 4a = 7.6 + 5a
a = 3.5m/s squared.
 
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You've not considered all the forces acting down the slope on m1.
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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