Working out tension of string holding a ball underwater

In summary, the conversation is about a physics homework question involving a submerged ball in a swimming pool. The volume of the ball is given and the task is to calculate the tension in each string that is attached to the bottom of the pool. The hint given is to look up the density of water. The conversation then discusses the different forces acting on the ball, including gravitational force, buoyancy force, and tension forces. The final conclusion is that a force balance needs to be done and the forces must be equal as the ball is not moving.
  • #1
Alice Martin
2
0
I have a physics homework question that i need help with;
A submerged ball of negligible mass is attached to the bottom of a swimming pool by two strings as shown. The volume of the ball is 5000cm^3. Calculate the tension in each string. (hint you need to look up the density of water)

How do i do this? Do i use the buoyancy of the ball or the tension formula?

The
Screen Shot 2016-04-25 at 4.13.49 pm.png
triangle with the base being the bottom of the pool and the ball being attached to the top vertex with a 60 degree angle
 
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  • #2
What you need to do is a force balance on the ball. :wink:

So there is a gravitational force, a buoyancy force and tension forces all acting on the ball, which is not moving. What does that tell you?
 
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Likes Alice Martin
  • #3
mfig said:
What you need to do is a force balance on the ball. :wink:

So there is a gravitational force, a buoyancy force and tension forces all acting on the ball, which is not moving. What does that tell you?
Thank you! That is a really simple way of putting it. I did not even think about the fact that the forces must be equal!:wink:
 
  • #4
Hi Alice! Welcome to PF!

I've gone ahead moved your thread to the homework forums, but in the future please make sure you place your question here (or in whichever homework forum is appropriate) and that you fill in the template provided when you create a thread in the homework forums.

@mfig, please use the report feature to report homework posts outside of the homework forums instead of replying to them. Thank you!
 

1. How does tension affect the string holding a ball underwater?

Tension in the string is what allows the ball to stay submerged underwater. It acts as a counterforce against the buoyancy force of the ball, keeping it from floating to the surface.

2. How do you calculate the tension of the string holding a ball underwater?

The tension of the string can be calculated using the formula T = mg - ρVg, where T is the tension, m is the mass of the ball, g is the acceleration due to gravity, ρ is the density of water, and V is the volume of the ball.

3. What factors can affect the tension of the string holding a ball underwater?

The tension of the string can be affected by the mass of the ball, the density of water, and the depth at which the ball is submerged. Changes in any of these factors can alter the tension and cause the ball to rise or sink in the water.

4. Can the tension of the string holding a ball underwater be too high?

Yes, if the tension is too high, it can cause the string to break or the ball to sink too deep in the water. It is important to calculate the appropriate tension based on the specific conditions of the experiment.

5. How can the tension of the string holding a ball underwater be adjusted?

The tension of the string can be adjusted by changing the mass of the ball, the depth at which it is submerged, or the density of the water. However, it is important to carefully calculate and monitor these changes to maintain the desired tension.

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