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How to Solve Newton's 3rd Law Pulley Problems?
- Thread starter HydroMarioUSA
- Start date
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- Law Newton 3rd law Pulleys String Weight
In summary, a user on physicsforums is looking for guidance on how to start a problem, as direct answers are not allowed. Another user suggests getting a free body diagram for each block and finding the tension in T3 and T2 to solve for m2. The original user then asks for clarification on how to use the forces to solve for m2, to which the second user explains how the tension in T3 affects the forces on the blocks. Finally, the original user confirms their answer as D, which was obtained by subtracting the forces of gravity on T1 and T3 from the tension in T1 and dividing by 9.8.
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HydroMarioUSA
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Apparently, it's against the rules to just ask for answers, but could someone tell me where to start?
- #3
Biker
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Hello, Welcome to physicsforums 
.Yes, It is against the rules to give direct answer. We can only give where to start from and the rest is on you.
Massless means that the tension is the same along the string. So what you need to do is to get the free body diagram for each block. Try to find the tension in T3 and T2 then get m2
.Yes, It is against the rules to give direct answer. We can only give where to start from and the rest is on you.Massless means that the tension is the same along the string. So what you need to do is to get the free body diagram for each block. Try to find the tension in T3 and T2 then get m2
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HydroMarioUSA
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How do you get m2 from knowing T3 and T2, sorry if it's obvious?
- #5
Biker
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What do you get from analyzing the forces on M2?HydroMarioUSA said:How do you get m2 from knowing T3 and T2, sorry if it's obvious?
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HydroMarioUSA
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Net force, right?
OH I see thanks!
OH I see thanks!
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HydroMarioUSA
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Would T3 = Fg on m3 and T2 = Fg on m2 + Fg on m3? Is that how it works?
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Biker
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Yes, That Fg on m3 comes from the tension in T3 it pulls up m3 and pulls downward on M2 so that M2 can pull it up :)HydroMarioUSA said:
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HydroMarioUSA
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Is the answer (D)? The way I got it was by knowing that T1 = 182.28, and subtracting that by the forces of gravity on T1 and T3, then finally dividing that by 9.8...
- #10
Biker
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Yes the answer is D.HydroMarioUSA said:
FAQ: How to Solve Newton's 3rd Law Pulley Problems?
What is Newton's 3rd Law?
Newton's 3rd Law states that for every action, there is an equal and opposite reaction. This means that when an object exerts a force on another object, the second object will exert an equal and opposite force back on the first object.
How does Newton's 3rd Law apply to pulleys?
In the context of pulleys, Newton's 3rd Law means that the tension in the rope on one side of the pulley is equal to the tension on the other side. This is because as one side of the rope pulls down on the pulley, the other side must also pull up with an equal force in order to maintain equilibrium.
Can Newton's 3rd Law be violated with pulleys?
No, Newton's 3rd Law is a fundamental law of physics and cannot be violated. In the case of pulleys, the forces may appear unequal due to the weight of the rope or friction, but the overall forces are still equal and opposite.
How does the number of pulleys affect the force needed to lift an object?
The number of pulleys used in a system can affect the force needed to lift an object. Using more pulleys can distribute the load and reduce the force needed to lift the object. This is because each pulley reduces the weight by a certain amount, making it easier to lift.
Can pulleys be used to create more force?
No, pulleys do not create more force. They simply redirect the force applied in a certain direction, making it easier to lift an object. The overall force remains the same, but the work is distributed over a larger distance.