Circular Motion Problem: Finding Tension in a Vertical Circle [11.8 N]

In summary, the object of mass 0.20 kg tied to a string is moving in a vertical circle. At the highest point, the tension in the string is zero and the centripetal force is equal to the weight. At the lowest point, the tension is the sum of the centripetal force and the weight, which is equal to twice the weight. To find the tension at the lowest point, the law of conservation of energy can be used.
  • #1
PhysicStud01
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Homework Statement


object of mass 0.20 kg tied to a string is made to move in a vertical circle. When the object is at the highest point, the tension in the string is zero. Determine the tension in the string when the object is at the lowest point. [11.8 N]

Homework Equations

The Attempt at a Solution


i tried it and could not arrive at the state answer in bracket. at highest point, weight + tension gives the centripetal force. since tension is said to be zero, at the hioghest point, weight = centripetal force.

then at lowest point, tension - weight gives centripetal. tension is the sum of centripetal and weight = 2 x weight since centripetal was calculated to be equal to weight. but this is not the answer given.
am i missing something?
 
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  • #2
Your right about the first part. But the centripetal force acting on the body is not a constant.

At the highest position
T=0
mg = v²/r
v =√gr
this velocity is not the same velocity which it has at the lowest position
To calculate that use the law of conservation of energy :
½mv²highest position = ½mv²lowest position + mg(2r)
and then find your tension.
 
Last edited:
  • #3
Suraj M said:
<snips>
T = 11.8 N
okay? :oldsmile:

You did pretty much the entire problem. You did it well but you did too much. Let the OP do his own homework and just give hints.

I know there is an urge to leap out and solve the problem. I have the same urge. But once you solve it, don't post the entire thing. If you do the entire thing for them they won't get the benefit of the homework.
 
  • #4
DEvens said:
You did pretty much the entire problem. You did it well but you did too much. Let the OP do his own homework and just give hints.

I know there is an urge to leap out and solve the problem. I have the same urge. But once you solve it, don't post the entire thing. If you do the entire thing for them they won't get the benefit of the homework.
ok DEvens .. i realized that and edited it ..and sorry.
 
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Likes DEvens
  • #5


Your approach is correct, but there may be a mistake in your calculations. The tension at the lowest point should be equal to the sum of the weight and the centripetal force, not double the weight. Double-check your calculations and equations to see if there was a mistake made. It's also possible that the given answer of 11.8 N may be incorrect.
 

1. What is circular motion?

Circular motion is the movement of an object along a circular path, where the object maintains a constant distance from a fixed point.

2. What are some examples of circular motion?

Some examples of circular motion include the rotation of a spinning top, the motion of a Ferris wheel, and the orbit of planets around the sun.

3. How is centripetal force related to circular motion?

Centripetal force is the force that keeps an object moving in a circular path. It acts towards the center of the circle and is responsible for continuously changing the direction of an object's velocity.

4. How do you calculate the speed of an object in circular motion?

The speed of an object in circular motion can be calculated using the formula v = 2πr/T, where v is the speed, r is the radius of the circle, and T is the time it takes to complete one full revolution.

5. What is the difference between uniform circular motion and non-uniform circular motion?

In uniform circular motion, the speed of the object remains constant, while in non-uniform circular motion, the speed changes as the object moves along the circular path. In non-uniform circular motion, the centripetal force is not constant, causing the object to accelerate or decelerate.

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