How Is Tension Calculated in a Pulley System with Unequal Masses?

  • Thread starter Thread starter Notyou
  • Start date Start date
  • Tags Tags
    Pulley Tension
AI Thread Summary
In a pulley system with unequal masses, the tension in the string and the acceleration of each mass can be determined using Newton's second law, F=ma. The discussion revolves around two masses, 12kg and 10kg, where the net forces acting on each mass are analyzed through free body diagrams. The tension acts differently on each mass due to their distinct weights, leading to confusion about how forces are applied independently versus in a combined system. The participant ultimately realizes that the forces acting on the masses in the pulley system are independent, contrasting with a scenario where blocks are pulled together on a flat surface. Understanding these dynamics is crucial for solving tension problems effectively.
Notyou
Messages
9
Reaction score
0

Homework Statement


Two objects are hanging from a pulley. One has a mass of 12kg and another has a mass of 10kg. Initially, the two masses are at rest and friction is ignored. Once in motion, find the tension in the string and the acceleration of each of the two masses.

Homework Equations


F=ma

The Attempt at a Solution


Ok... another tension problem. I'm really having an extremely hard time understanding the concept of tension. For this problem I drew the free body diagrams of both masses. The mass of 12kg is m1 and the mass of 10kg is m2.
For m1, the force in the negative y direction (pulling the object to the ground) is the weight, or the mass times acceleration. The mass pulling on m1 in the positive direction is the tension.
For m2, the force pulling in the negative y direction is the weight. The force pulling in the positive y direction is the tension and the weight of m1.
The net force acting on m1 would be... m1g-T=(m1 + m2)a
The net force acting on m2 would be... T+m1g=m2a

Something in that train of thought is wrong. I believe it is the net force acting on m2 or maybe even the force acting on m2 in the positive y direction. Any help would be greatly appreciated.
 
Physics news on Phys.org
Figured it out <_<. The force was acting on the objects independently. What I don't really understand though, is how come in this scenario the same force is acting independently on the objects but if I laid the two blocks on a flat surface and pulled the heavier block with a string the force would be acting on their combined weight?
 
Thread 'Variable mass system : water sprayed into a moving container'

Thread 'Variable mass system : water sprayed into a moving container'

Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
View full post »

Thread 'Egg Drop Challenge! Need ideas for winning designs'

I was thinking using 2 purple mattress samples, and taping them together, I do want other ideas though, the main guidelines are; Must have a volume LESS than 1600 cubic centimeters, and CAN'T exceed 25 cm in ANY direction. Must be LESS than 1 kg. NO parachutes. NO glue or Tape can touch the egg. MUST be able to take egg out in less than 1 minute. Grade A large eggs will be used.
View full post »

Similar threads

Particle dynamics (mechanics): inclined plane, pulley, two blocks
Replies
14
Views
2K
Halliday, Resnick & Krane Chapter 5: Force on Pulley
Replies
1
Views
2K
Newton's Second Law (Pulley Sustem)
Replies
3
Views
2K
Acceleration of rising mass and tension in cord
Replies
33
Views
3K
Accelerating pulleys (3 pulleys and 3 masses)
Replies
5
Views
2K
Problem with two pulleys and three masses
3
Replies
102
Views
7K
Olympiad dynamics problem with 3 masses and a pulley
Replies
17
Views
2K
Find the acceleration of the system (2 blocks sliding on a table)
Replies
23
Views
2K
3 pulley problem with attached masses
Replies
15
Views
6K
Tension in a string connecting two blocks having equal and opposite velocities
Replies
21
Views
371

Hot Threads

Recent Insights

Back
Top