rotational forces

[rainashley]

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If you are spinning a ball around in a circle that's attached to a string over your head, what are the forces acting on the ball?
I know there is the force (tension) that your holding
what else is there?
thanks

 

[PiBond]

If you are spinning a ball around in a circle that's attached to a string over your head, what are the forces acting on the ball?
I know there is the force (tension) that your holding
what else is there?
thanks

gravity

 

[rainashley]

so its just two forces? gravity (mg) and the tension?
thats it?

 

[PiBond]

so its just two forces? gravity (mg) and the tension?
thats it?

yeah, but the speed is not constant (this is assuming that the object is being swung in a vertical circle)--unless you are swinging lasso style over your head

 

[rainashley]

yes
i am talking about lasso style over my head
the ball is moving in a circle over my head
(centripetal force style)
then what?

 

[PiBond]

yes
i am talking about lasso style over my head
the ball is moving in a circle over my head
(centripetal force style)
then what?

Assuming you're given the angle and asked to find Tension, solve for tension using the formula Tsine(theta)=mg (note that we are using the y-direction first because the forces are zero due to no acceleration in this direction)

Once you find tension then you should be able to find the speed. For centripetal acceleration questions ask yourself: what is providing the centripetal force to cause the object to accelerate centripetally (v^2/r)? In this case it's the x-component of the tension that's causing the object to rotate (Tcos(theta)). Use the formula Tcos(theta)=m(v^2/r)

 

[rainashley]

Assuming you're given the angle and asked to find Tension, solve for tension using the formula Tsine(theta)=mg (note that we are using the y-direction first because the forces are zero due to no acceleration in this direction)

Once you find tension then you should be able to find the speed. For centripetal acceleration questions ask yourself: what is providing the centripetal force to cause the object to accelerate centripetally (v^2/r)? In this case it's the x-component of the tension that's causing the object to rotate (Tcos(theta)). Use the formula Tcos(theta)=m(v^2/r)

i just want to know the different types of forces acting on the ball
a ball is spun in a circle attached to a string over my head in a horizontal circular fashion
what are the different forces acting on it?
i know one is tension that is towards the center of the movement
what else is there? what other forces?
how many forces are acting on the ball total?
thanks

 

[PiBond]

i just want to know the different types of forces acting on the ball
a ball is spun in a circle attached to a string over my head in a horizontal circular fashion
what are the different forces acting on it?
i know one is tension that is towards the center of the movement
what else is there? what other forces?
how many forces are acting on the ball total?
thanks

...we already talked about the gravity acting on it (see post #2, 3, 4).

Tension + gravity = forces acting on the ball

 

[rainashley]

theres no force in the velocity direction?

 

[Seraph 84]

theres no force in the velocity direction?

The direction of the velocity vector is independent of the direction of the force vector. Just because a ball is flying horizontally through the air doesn't mean there is a force in that same direction.

In this example, there is only the F(T) acting inward and F(g) acting downward.

 

[rainashley]

what about air resistance?

 

[PiBond]

what about air resistance?

it's not there unless the problem says so.

 

[rainashley]

The tangental force is 0 in uniform circular motion... right?
does this apply here?