Forces involved in circular motion

In summary, when a ball on the end of a string is swung horizontally in circular motion, there is a centripetal acceleration which is provided by the tension acting as the centripetal force and acting along the radius of the circular path. The reaction force of the tension acting on the string is the ball pulling on the string, in accordance with Newton's third law. This reaction force is not the same as centrifugal force, which is a special "fictitious" force used when analyzing things from a rotating frame.
  • #1
scottnobles
2
0

Homework Statement


hey, i was looking at an explanation in a textbook where it says a ball on the end of a string is swung horizontally in circular motion. There is a centripetal acceleration therefore tension acts as the centripetal force and acts along the radius of the circular path. What i want to know is that Newtons third law states that every action has an opposite and equal reaction. So what is the reaction force of the tension acting on the string?


Homework Equations



F=mv^2/r

The Attempt at a Solution


I can't seem to be able to figure out what it is but i think mass would not be the reaction force because mass is a scaler and has no direction. The other explanation would be centrifugal force but isn't centrifugal force a reaction force of centripetal force? which is what I am trying to find? This is why I am a little confused.
 
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  • #2
Forget centrifugal force--that's a special "fictitious" force used when analyzing things from a rotating frame. (You probably won't use that until you get to a more advanced class.)

Instead, just use the most basic form of Newton's 3rd law: If A exerts a force on B, then B exerts an equal and opposite force on A. If the string pulls the ball, the ball pulls the string.
 
  • #3


I can explain the forces involved in circular motion using the principles of classical mechanics. In this scenario, the ball on the end of the string is experiencing a centripetal force, which is the force that keeps an object moving in a circular path. This force is directed towards the center of the circular motion and is provided by the tension in the string. This means that the tension in the string is the action force, and the reaction force is the centripetal force.

According to Newton's third law, every action has an equal and opposite reaction. In this case, the reaction force of the tension acting on the string is the centrifugal force. This force is an apparent force that appears to pull the object away from the center of rotation. It is not a real force, but rather a result of the object's inertia trying to keep it moving in a straight line while the string forces it to move in a circular path.

In summary, the tension in the string is the centripetal force, and the centrifugal force is the reaction force to this tension. It is important to note that these two forces are not equal in magnitude, but they are equal in opposite directions, as stated by Newton's third law. I hope this explanation helps clarify any confusion you may have had about the forces involved in circular motion.
 

1. What is circular motion?

Circular motion is the movement of an object along a circular path at a constant speed. It involves a continuous change in direction, but the object's speed remains constant.

2. What forces are involved in circular motion?

There are two main forces involved in circular motion: centripetal force and centrifugal force. Centripetal force is directed towards the center of the circle and keeps the object moving along the circular path. Centrifugal force is the equal and opposite reaction to centripetal force, and is directed away from the center of the circle.

3. How is centripetal force calculated?

The formula for centripetal force is Fc = (mv^2)/r, where Fc is the centripetal force, m is the mass of the object, v is the speed of the object, and r is the radius of the circular path.

4. What factors affect the amount of centripetal force?

The amount of centripetal force is affected by the mass of the object, the speed of the object, and the radius of the circular path. The greater the mass and speed of the object, or the smaller the radius of the circular path, the greater the centripetal force required to keep the object in circular motion.

5. Can an object in circular motion have a constant speed and changing velocity?

Yes, an object in circular motion can have a constant speed but changing velocity. This is because velocity not only takes into account the speed of the object, but also the direction of motion. In circular motion, the direction of motion is constantly changing, so the velocity is also constantly changing even if the speed remains constant.

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