Solving 2 Mass System w/o Diagram: Find Acceleration, Force & Time

AI Thread Summary
The discussion centers on solving a physics problem involving two connected masses (0.5kg and 0.8kg) over a frictionless pulley, focusing on finding acceleration, net force, and time to reach a specific velocity. Participants emphasize the importance of free body diagrams to visualize forces acting on each mass, which aids in applying Newton's laws effectively. It is noted that the system's acceleration can be calculated using the difference in weights and the total mass, assuming the pulley is fixed and does not spin. The conversation highlights that while a diagram would enhance understanding, the problem can still be approached conceptually without one. Overall, the analysis revolves around the dynamics of the two-mass system and the assumptions necessary for solving the problem accurately.
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Homework Statement


Two objects of mass 0.5kg and 0.8kg respectively are connected by a light string that passes over a frictionless pulley. Find:
a) the acceleration of the 0.5kg mass
b) the net force acting on the 0.8kg mass
c) the time taken for the masses to reach a velocity of 2.8m/s


Homework Equations


Newton's laws


The Attempt at a Solution


The question was given without a diagram. Is it possible to do this problem just from the data above without a diagram?
 
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pivoxa15 said:

Homework Statement


Two objects of mass 0.5kg and 0.8kg respectively are connected by a light string that passes over a frictionless pulley. Find:
a) the acceleration of the 0.5kg mass
b) the net force acting on the 0.8kg mass
c) the time taken for the masses to reach a velocity of 2.8m/s


Homework Equations


Newton's laws


The Attempt at a Solution


The question was given without a diagram. Is it possible to do this problem just from the data above without a diagram?
A diagram would be helpful. I believe the problem assumes a pulley attached to a ceiling, with the masses hanging down from either side. The 0.8 kg mass will move downward, and the 0.5 kg mass moves up. Draw free body diagrams of each mass and identify the forces acting on each, then apply Newton 2 to determine the acceleration of each from the net force acting on each.
 
Object 1: 0.5 kg
Object 2: 0.8 kg

Tension relates the two objects =).

There needs to be a force body diagram to get an idea of how the forces are working. But, without it you can get a basic idea of how it looks in your head and be able to solve it.

Acceleration of the system = [ (object 1 - object 2) / (object 1 + object 2) ] * gravity

1/2mv^2 and mgh are your tools when dealing with energy =). They can also be tied with vectors.

Using the equations: x = xo + vot + 1/2at^2, v2^2 = v2o^2 + 2a(x2 - x1) and v = vo + at.

It is possible.
 
PhanthomJay said:
A diagram would be helpful. I believe the problem assumes a pulley attached to a ceiling, with the masses hanging down from either side. The 0.8 kg mass will move downward, and the 0.5 kg mass moves up. Draw free body diagrams of each mass and identify the forces acting on each, then apply Newton 2 to determine the acceleration of each from the net force acting on each.

The answers did assume that the weights were spread from both sides downwards. Each mass has the same acceleration and tension because they are connected by strings so are considered linked. We assume the string cannot be stretched nor dangled do we?
 
pivoxa15 said:
The answers did assume that the weights were spread from both sides downwards. Each mass has the same acceleration and tension because they are connected by strings so are considered linked. We assume the string cannot be stretched nor dangled do we?
Right, and we assume the pulley does not actually spin. When the pulley rotates, you have to factor in friction and moment of inertia of the wheel
 
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