Calculating Acceleration in an Inclined Force Problem with Pulley Setup

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SUMMARY

The discussion focuses on calculating the acceleration of a system involving two masses, M1 (5 kg) and M2 (4 kg), with a coefficient of friction of 0.20 on an inclined plane at a 40-degree angle. The teacher indicated that the correct acceleration is 0.02 m/s², but the participant calculated 3.5 m/s² using the equations T−mg=ma and T−Ff=ma. The participant's confusion stemmed from not accounting for all forces acting on M1 down the slope. Properly applying the equations and considering all forces is essential for accurate results.

PREREQUISITES
  • Understanding of Newton's Second Law of Motion
  • Familiarity with inclined plane physics
  • Knowledge of frictional force calculations
  • Ability to solve simultaneous equations
NEXT STEPS
  • Review the derivation of forces on inclined planes
  • Learn about tension in pulley systems
  • Study the effects of friction on motion
  • Practice solving problems involving multiple masses and forces
USEFUL FOR

Students studying physics, particularly those focusing on mechanics, as well as educators looking to clarify inclined plane problems and tension in pulley systems.

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.
 

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