Net Force at the Bottom of Circular Motion

In summary, when an object is being swung vertically on a stick, the net force at the bottom can be found by adding the centripetal force, which is equal to the mass times the velocity squared divided by the radius, to the force of gravity. This is because the centripetal force is provided by both the tension of the string and the force of gravity. The equation for calculating the net force is Fnet = mv^2/r.
  • #1
marvolo1300
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Homework Statement


An object is being swung vertically on a stick. What is the net force at the bottom?

The mass of the object = 2kg.
g= 9.81ms-1.
v = 6ms-1 at the bottom.



Homework Equations


F= mg
Fcentripetal = (m*v^2)/r


The Attempt at a Solution


I just need to know if i must add the force of gravity to the centripetal force.


Thank you.
 
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  • #2
Thanks anyways. I solved it.

For anyone that is looking for an answer:

Yes, you must add the centripetal force to the force of gravity. This is because the centripetal force in this example is found through the velocity, rather than through the acceleration due to gravity.
 
  • #3
But the net force at the bottom IS the centripetal force, mv^2/r. You don't add anything to it to get the net force, which is what the problem seems to be asking.
 
  • #4
Thank you PhantomJay.

The centripetal force in this problem is provided by the tension of the string and also the force of gravity.

So, Fnet = m*g + (m*v^2)/r
 
  • #5
marvolo1300 said:
Thank you PhantomJay.

The centripetal force in this problem is provided by the tension of the string and also the force of gravity.
yes, correct
So, Fnet = m*g + (m*v^2)/r
No, that is not correct. Fnet = mv^2/r

The gravity force acts down, and the tension in the wood stick acts up. And the centripetal force acts up toward the center of the circle.

Shoudn't it be

[itex] F_{net} = T - mg = mv^2/r [/itex] ?
 

FAQ: Net Force at the Bottom of Circular Motion

1. What is the net force at the bottom of circular motion?

The net force at the bottom of circular motion is the sum of all the forces acting on an object at the bottom of a circular path. This includes the centripetal force, which is directed towards the center of the circle, and any other external forces such as gravity or friction.

2. How is the net force at the bottom of circular motion calculated?

The net force at the bottom of circular motion can be calculated using the formula F_net = F_centripetal + F_external, where F_centripetal is the centripetal force and F_external is the sum of all other external forces acting on the object.

3. Is the net force at the bottom of circular motion always zero?

No, the net force at the bottom of circular motion is not always zero. It is only zero if the centripetal force is equal in magnitude and opposite in direction to the sum of all other external forces. If this is not the case, there will be a net force acting on the object.

4. How does the net force at the bottom of circular motion affect the speed of the object?

The net force at the bottom of circular motion affects the speed of the object by changing its direction or magnitude. If the net force is directed towards the center of the circle, it will cause the object to continue moving in a circular path at a constant speed. If the net force is not directed towards the center, it will cause the object to speed up or slow down depending on the direction and magnitude of the force.

5. Can the net force at the bottom of circular motion be greater than the centripetal force?

Yes, the net force at the bottom of circular motion can be greater than the centripetal force. This can happen if the sum of all other external forces is greater than the centripetal force, causing a net force in the direction of those forces. In this case, the object will not move in a circular path and may even accelerate away from the center of the circle.

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