Finding Tension in a Massless String on an Inclined Plane

In summary, the conversation involves a problem involving objects attached to spring balances and an inclined plane. The question is how to determine the readings of the spring balances given certain conditions. The person asking for help tried two different approaches but was unsure of their calculations. With the help of others, it was discovered that the component of weight parallel to the incline was determined incorrectly. A correct solution was found by drawing a correct free body diagram.
  • #1
toboldlygo
32
2

Homework Statement


In the figure below, the objects are attached to spring balances calibrated in Newtons. Give the readings of the balances in each case, assuming that the strings are massless and the incline is frictionless.

04-34.gif


I need help with (d). If the picture's too grainy to read off the values, the two blocks weight 10 kg each, the angle is 30 degrees, and the sides are 5.2 m (right above the (d)) and 3 m.

Homework Equations


[/B]
F = ma, with Σ F = 0

The Attempt at a Solution


[/B]
So, I know the reading off the balance will be equivalent to the tension in the string. I've tried doing this problem two different ways: first, I found the total Weight force (98.1 N) and used the sin to find the hypotenuse, which was 196.2 N. Then, when that was wrong, I thought maybe I should use gravity, split it into components, and then multiply whatever the hypotenuse of that right triangle was by the mass. I got 196.2 N again. What am I doing wrong? I've drawn a free body diagram and everything, but I don't know what I'm doing wrong here. I have a suspicion I'm not drawing the forces correctly, but I'm not sure. Thanks in advance for any help!
 
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  • #2
How can the spring balance give a value greater than the weight of the block?

Maybe show your FBD and your calcs.
 
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  • #3
You determined the component of the weight parallel to the incline incorrectly.

Chet
 
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  • #4
I think I figured it out. I was drawing my triangle incorrectly (the amount of silly mistakes I make when doing physics problems...). Thanks for the sanity check, paisiello2, and for hinting at what was probably wrong, chestermiller. I appreciate it!
 

1. What is tension and how is it related to forces?

Tension is a force that is created when an object is pulled or stretched. It is always directed along the length of the object and is equal in magnitude to the force being applied. Tension is related to forces in that it is one of the types of forces that can act on an object.

2. How do you calculate tension in a system?

To calculate tension in a system, you need to know the mass of the object, the acceleration due to gravity, and the angle of the rope or string. You can then use the formula T = mgcosθ, where T is the tension, m is the mass, g is the acceleration due to gravity, and θ is the angle of the rope or string.

3. What is the difference between tension and compression?

Tension is a force that pulls or stretches an object, while compression is a force that pushes or squeezes an object. Tension and compression are equal in magnitude but have opposite directions. Both types of forces can be found in structures such as bridges and buildings.

4. How does tension affect the stability of a structure?

Tension can affect the stability of a structure by either strengthening or weakening it. In some cases, tension can help distribute the weight of a structure more evenly, making it more stable. However, if there is too much tension, it can cause the structure to collapse. Proper design and engineering are crucial to ensure the right amount of tension is present in a structure.

5. Can tension be negative?

No, tension cannot be negative. It is always a positive force that acts in the direction of the pull or stretch on an object. If a negative value is calculated for tension, it means that the direction of the force is opposite to what was assumed, and the magnitude should be corrected accordingly.

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