Accel of 2 Masses & 3 Pulleys: F=Ma Solution

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In summary: This thread was about the algebraic relationship between the two accelerations, which has nothing to do with the forces. It follows entirely from the constancy of the total string length.
  • #1
Gbox
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Homework Statement



Find the acceleration of the masses
PAAcdkT.jpg


Homework Equations


##F=Ma##

The Attempt at a Solution


We know that the system is moving so for ##M_1## we have ##M_1gsin\theta## on the other hand on ##M_2## we have ##M_1gsin\theta-M_2gsin\theta##

How can I conclude that the acceleration of ##M_2## is twice of ##M_1##?
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  • #2
Gbox said:
How can I conclude that the acceleration of M2 is twice of M1?
I assume you meant the other way around.
It follows from the assumption that the string length does not change.
 
  • #3
haruspex said:
I assume you meant the other way around.
It follows from the assumption that the string length does not change.

Sorry ##M_1## is twice the acceleration as ##M_2##.

Yes the string length does not change
 
  • #4
Gbox said:
Sorry ##M_1## is twice the acceleration as ##M_2##.

Yes the string length does not change
Do you see how it follows from that?
 
  • #5
haruspex said:
Do you see how it follows from that?
No I can't understand the forces map
 
  • #6
Gbox said:
No I can't understand the forces map
It's not to do with the forces. Consider the lengths of the three sections of strings. They add up to a constant, and two are always the same as each other. That allows you to express two in terms of the third. Then see how they relate to the two accelerations.
 
  • #7
haruspex said:
It's not to do with the forces. Consider the lengths of the three sections of strings. They add up to a constant, and two are always the same as each other. That allows you to express two in terms of the third. Then see how they relate to the two accelerations.
Can you show me the free body diagram of the forces acting in the system
 
  • #8
Crystal037 said:
Can you show me the free body diagram of the forces acting in the system
This thread was about the algebraic relationship between the two accelerations, which has nothing to do with the forces. It follows entirely from the constancy of the total string length.
If you want to discuss the free body diagrams for this problem, post it as a new thread with your own attempt.
 

1. What is the formula for calculating the acceleration of two masses connected by three pulleys?

The formula for calculating the acceleration of two masses connected by three pulleys is F=ma, where F is the net force acting on the system, m is the total mass of the system, and a is the resulting acceleration.

2. How do the pulleys affect the acceleration of the system?

The pulleys in this system act as a mechanical advantage, allowing the force to be distributed and reducing the amount of force needed to move the masses. This results in a greater acceleration of the system.

3. Can the acceleration of the system be negative?

Yes, the acceleration of the system can be negative if the net force acting on the system is in the opposite direction of the initial motion of the masses. This would result in the masses decelerating.

4. How does the placement of the pulleys affect the acceleration of the system?

The placement of the pulleys can affect the acceleration of the system by changing the direction and distribution of the forces acting on the masses. Placing the pulleys closer together can increase the acceleration, while placing them further apart may decrease the acceleration.

5. Can this formula be applied to systems with more than two masses and three pulleys?

Yes, the F=ma formula can be applied to systems with more than two masses and three pulleys. However, the calculations may become more complex as more masses and pulleys are added.

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