Massless strings/pulleys: Finding the magnitude of the Force

AI Thread Summary
To find the magnitude of force F required to lift a 10.3 kg mass at constant speed using a massless string and frictionless pulleys, the key factors to consider are the weight of the mass and the tension in the string. Since the mass is lifted at a constant speed, the net force is zero, meaning the upward force F must equal the downward gravitational force (weight) acting on the mass. The weight can be calculated using the equation W = mg, where g is the acceleration due to gravity. The discussion emphasizes the need for a force equation rather than energy equations, as the problem focuses on force balance rather than work done. Understanding the setup and applying the correct formulas will lead to the solution.
Graphire
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Homework Statement


A massless string runs around two massless, frictionless pulleys, as shown in the figure below. An object with mass m = 10.3 kg hangs from one pulley. A force F is exerted on the free end of the string. What is the magnitude of the force F if the object is lifted at a constant speed?


Homework Equations


I'm guessing around 1/2m x v^2 but I really don't have a clue...


The Attempt at a Solution


Well so far I got that the force goes in the y-axis so that he factors involving the y-axis is the weight and tension. Since the question does not give me tension and I really don't know what formula to use to figure it out I'm quite lost.

There's also a diagram but I don't know how to put it up here...
 
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Graphire said:

Homework Statement


A massless string runs around two massless, frictionless pulleys, as shown in the figure below. An object with mass m = 10.3 kg hangs from one pulley. A force F is exerted on the free end of the string. What is the magnitude of the force F if the object is lifted at a constant speed?

Homework Equations


I'm guessing around 1/2m x v^2 but I really don't have a clue...

The Attempt at a Solution


Well so far I got that the force goes in the y-axis so that he factors involving the y-axis is the weight and tension. Since the question does not give me tension and I really don't know what formula to use to figure it out I'm quite lost.

There's also a diagram but I don't know how to put it up here...

Can you try to describe the figure? Give the path of the string and position of the pulleys and mass, if you can.

Also, (1/2) m * v2 will give you units of work or energy. It sounds more like you need an equation dealing with force, mass, and acceleration.
 
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