Solving a Tension Problem with 9 kg Handing Weight & 5 kg Block

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In summary, the conversation discusses a problem involving a hanging weight and a sliding block connected by a string over a pulley. The person is seeking help with finding the tension in the string and recalls their teacher mentioning turning a similar problem into one on the X-axis. They initially tried to calculate the tension using the weight and frictional force, but were unsure if this was correct. It is clarified that if there were no friction force, there would be no tension on the rope.
  • #1
tristan_fc
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I believe that I was late the day my instructor explained this type of problem in class, and my textbook is worthless, so I thought I would give this a shot. It's just a tension problem, but I don't know for sure how to do it.

A 9.00 kg handing weight is connected by a string over a pulley to a 5.00 kg block that is sliding on a flat table. If the coefficient of kinetic friction is 0.187, find the tension in the string.

I believe that tension is the sum of all forces on the rope correct? I recall my teacher saying that we could turn a similar problem into a problem on the X-axis by making gravity a force pulling on the block in the x-direction. Anyway, I thought that I would just do 9*9.8+-(5*0.187), but that didn't seem right to me because it would seem that a frictional force would increase the tension and not decrease it? I appreciate any help.

-Tristan
 
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  • #2
eh... I posted my question in the wrong section and they moved it here. I'm actually in Engineering Physics I in college, but I guess it doesn't matter where the question is if I get help.
 
  • #3
Yes, frictional force would increase tension, not decrease it.
However, if there were NO friction force, there would be NO tension on the rope, not the "9*9.9" you have. If there were no friction force the block would move freely. The tension on the rope IS the friction force.
 

1. How do you calculate the tension force in a system with a 9 kg hanging weight and a 5 kg block?

The tension force in this system can be calculated using Newton's Second Law of Motion, which states that the net force acting on an object is equal to its mass multiplied by its acceleration. In this case, the net force is the sum of the tension force and the weight of the hanging weight and block. Therefore, the equation would be: Tension force = (9 kg + 5 kg) x acceleration. We can also use the equation Tension force = mass x gravity, where gravity is the acceleration due to gravity (9.8 m/s^2). So, the tension force would be (9 kg + 5 kg) x 9.8 m/s^2 = 137.2 N.

2. How does the angle of the rope affect the tension force in a system?

The angle of the rope can have a significant impact on the tension force in a system. As the angle increases, the tension force also increases. This is because the weight of the hanging weight and block is distributed among both the horizontal and vertical components of the rope. As the angle increases, the horizontal component decreases while the vertical component increases, resulting in a larger tension force.

3. What is the difference between tension force and weight?

Tension force and weight are two different types of forces. Weight is the force exerted by a mass due to the acceleration of gravity. It is always directed downwards towards the center of the Earth. Tension force, on the other hand, is the force exerted by a string, rope, or cable when it is pulled at both ends. It is always directed along the length of the string and is dependent on the mass of the object and the angle of the rope.

4. Can the tension force ever be greater than the weight of the hanging weight and block?

Yes, the tension force can be greater than the weight of the hanging weight and block. This can happen when the angle of the rope is greater than 90 degrees. In this case, the vertical component of the tension force is larger than the weight of the hanging weight and block, resulting in a greater overall tension force.

5. What is the role of friction in a system with a tension force?

Friction plays a crucial role in a system with a tension force. It acts in the opposite direction of the tension force and can help to keep the rope in place. Without friction, the rope may slip or slide, resulting in an inaccurate measurement of the tension force. Additionally, friction can also affect the weight of the hanging weight and block, as it may be slightly less due to the opposing force of friction.

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