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Centripetal Motion.
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by vincentyuahyu90
on 2008-01-21 23:56:04
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My physic teacher have us a question. Basically it's from the newton second law. F=MA and it'll have related to this three thing. -Centripetal Acceleration -Centripetal force -Period of rotation the question is. If you have a bottle of hair jel in your hand, tried to turn around slowly, and if you do so, it'll move according to the centripetal acceration that's toward the center. However if you move it in circular motion but faster this time, the jel will move to side of bottle which will mov opposite to the centripetal force. Teacher want us to explain that situation using the above three or anyone. It's not about inertia as it'll explain only half of the situation. here's other situation where it's mostly the same. u r drinving a car. Putting ur handphone at the dash board you notic when you move to a sharp turn, the phone move toward outside of the curve. there's a pic tat i draw to show the situation. both of it can be explained by inertia but not all the observation can be explained. can someone tell me what's the explanation? http://i165.photobucket.com/albums/u57/vincentyu90/untitled-6.jpg |
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Re: Centripetal Motion.
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by
on 2008-01-22 01:12:15 (edited 2008-01-22 01:12:32)
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I hope I understand your question. The cell phone moving across the dash after a sharp turn seems to be satisfactorily explained by classical momentum. Of course, the phone stays in place on more gentle turns because of the force of friction. I don't use hair jell, but imagine it has high viscosity. Similar to friction, viscosity will impede flow, so that when a small force is applied, the jell appears normal. Only when a large enough force is applied to deform the jell does it squish to the outside of the spinning container. 
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Re: Centripetal Motion.
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by vincentyuahyu90
on 2008-01-23 20:04:25
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Well, your explaination does made sense but, my teacher wanted us to explain it wit the Centripetal Acceleration -Centripetal force -Period of rotation which i don't understand a bit about it. well it's ok then. i'll ask him myself for sure. thanks for trying helping out. |
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Re: Centripetal Motion.
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by Death Kamehameha
on 2008-05-07 08:16:07
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Hmm. Maybe its because of the external force exerted on the gel has a much larger magnitude of force compared to the cohesive force between gel molecules.. Therefore, External force > Centripetal force And this causes the gel to move to the sides Try thinking of the car speeding too fast on a sharp bend? The friction of tires between the road provide only so much centripetal force.. That when the car speeds up too fast, the friction decreases and the car skids.. Kinda similar to your gel thingy right? Use formula: since centripetal acceleration, a = v^2/r and F = ma, F. centripetal = m(v^2)/r r:radius of circle m:mass v:velocity assuming the tire only provides frictional force of 9kN, but at the speed you are driving at let's say 60mph, on a sharp bend with a small radius, This causes 'centripetal acc' to be very high.. And since F=ma, if 'a' increases, 'F' increases as well.. If 'F'>9kN! The car skids! For period, T T = 1/f = 2p/omega(w) 'p' as 'pi' used in circle formulas; w or omega is angular speed and w = v/r Another situation, small radius, large v, causes w to increases as w increases, T decreases, so if spun too fast, the period decreases but the frequency increases.. I hope you understand I'm not too good in explainin.. Wish me luck in my exams!! XD 2 weeks!
-Keough- |ãŸã„ れㄠãょã†|
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Re: Centripetal Motion.
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| I know that this topic is dead but it is worth of intrest that oil purifers on modern ships use the same concept to remove dirt and water from the oil. |
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Re: Centripetal Motion.
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by vincentyuahyu90
on 2008-06-08 10:10:13
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| 0.0 this thread still alive? anyway my teacher had already explained it to us. And yeah it's some sort of what death have explained. And dam good idea! You should suggest it to the oil manefacture company. XD |