Equations of Motion Homework: Acceleration of Block A

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SUMMARY

The discussion focuses on determining the acceleration of block A in a physics problem involving friction and pulleys. The user presents their equations, which include the forces acting on block A and block B, and seeks validation for their approach. Key equations include ƩFx = 2T + μmgcos60° - mgsin60° and the relationship aB = -2aA. The user realizes that the angle used in their calculations is incorrect, as it should be 30° instead of 60°.

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  • Understanding of Newton's laws of motion
  • Familiarity with friction coefficients and their calculations
  • Knowledge of trigonometric functions in physics contexts
  • Ability to set up and solve systems of equations
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  • Review the principles of Newton's second law of motion
  • Study the effects of friction in mechanical systems
  • Learn how to correctly apply trigonometric functions in physics problems
  • Practice solving systems of equations in dynamics problems
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Students studying physics, particularly those focusing on mechanics, as well as educators looking for examples of problem-solving in dynamics involving friction and pulleys.

aaronfue
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Homework Statement



I seem to be having trouble setting up my equations and not getting the correct answer to some of these problems.

Ex 1:
Determine the acceleration of block A when the system is released. The coefficient of friction and the weight of each block are indicated in the figure. Neglect the mass of the pulleys and cords. See attached image.

Homework Equations



m = [itex]\frac{lb}{32.2}[/itex]

So for my first set of equations on block A:
ƩFx = 2T+ μmgcos60° - mgsin60° = ([itex]\frac{lb}{32.2}[/itex])aA

ƩFy = N - mgcos60° = 0
N = mgcos60°

Ff = μ*N = μmgcos60°

Block B:
+[itex]\uparrow[/itex]
ƩFy = T - mg = ([itex]\frac{lb}{32.2}[/itex])aB

Pulley:
aB = -2aA

1. Are my equations correct?
2. Was I correct to use 60°? (I'm sure it is right but...I feel a bit doubtful.)
 

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Look at the picture. The angle is 30°.

ehild
 

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