Conceptual understanding of circular motion

AI Thread Summary
Centripetal force is not equal to a person's weight because it is determined by the net force acting towards the center of the circular path. The equation F = ma for radial motion shows that the centripetal force is the difference between gravitational force (mg) and the normal force (N). In non-rotational scenarios, this difference is zero, but during circular motion, the normal force is less than the gravitational force. The confusion arises from the common definition of weight as mg, while the actual weight felt is the normal force. Understanding this distinction clarifies the dynamics of circular motion.
cmwilli
Messages
6
Reaction score
0
[PLAIN]http://img207.imageshack.us/img207/37/capturebg.jpg



a=v^2/r
v=2pir/T
f=ma



So I already have the answers to all the questions. The problem I am having is I don't understand why the centripetal force is not equal to the weight of the person. If it isn't the weight what force, other than gravity, is acting on him that would be called the centripetal force.
 
Last edited by a moderator:
Physics news on Phys.org
hi cmwilli! :smile:
cmwilli said:
… I don't understand why the centripetal force is not equal to the weight of the person. If it isn't the weight what force, other than gravity, is acting on him that would be called the centripetal force.

i think the book is correct, but rather confusing

the F = ma equation for the radial (vertical) direction, for someone standing on the ground, is mg - N = mv2/r

the total centripetal force is the LHS, mg - N (so, for no rotation, it would be zero), but the weight (ie, what would show up if he was standing on a weighing machine) is the reaction force N, which is less than mg

the book is confusing because we usually call mg the weight, although technically our weight is what we feel, ie the reaction force, N, against us (which is usually the same as mg, but not in this case!) :smile:
 
What does LHS mean?
 
Left-hand side! :biggrin:

(of the equation)
 
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Thread 'Trying to understand the logic behind adding vectors with an angle between them'
My initial calculation was to subtract V1 from V2 to show that from the perspective of the second aircraft the first one is -300km/h. So i checked with ChatGPT and it said I cant just subtract them because I have an angle between them. So I dont understand the reasoning of it. Like why should a velocity be dependent on an angle? I was thinking about how it would look like if the planes where parallel to each other, and then how it look like if one is turning away and I dont see it. Since...
Back
Top