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2:01 pm, Oct 18 2011
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Okay, so anyone who likes physics...come 'ere!

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Okay, so here's a roller coaster display with various terms. Which one is incorrect and why? @_@ And for the right side of the roller coaster (my own question), is that a hill or is it just a turn? I have no clue. :'(
I'm thinking it's the free fall one, but then again, I don't know. So if anyone can help me out soon, thanks. xD

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Post #502006
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2:20 pm, Oct 18 2011
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It goes left to right, right? so potential energy first and kineticc energy last.

Have no idea which is wrong, but.
I don't get why velocity is placed (that just means km/h or m/s etc.)
Acceleration is on a weird spot (the free fall accelerates, the flat part only if there is a booster or something)

Post #502011
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3:01 pm, Oct 18 2011
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I'd also say free fall is the intruder. In simple terms, free fall is when an object is falling towards the earth's surface, and you have a "ramp" there. So friction would be right instead of free fall.

And on the right side, it's a turn, I guess. If yes, then centripetal acceleration is right. You should ask your professor, my logic tells me it's a turn if there's only one wrong answer in the diagram. smile

I could be wrong, it's been a while since I studied anything related to physics.

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his and her sonnet
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3:17 pm, Oct 18 2011
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please forget about that picture
it will confuse the hell out of you, and its not a very good representation of the graphs.
free fall is incorrect
assuming that the ball is thrown downwards from a certain height. the graph should be increasing(the gradient is acceleration) so the graph should be curve-like and going upwards until it reaches maximum height.
also note that the "gravitation" label is incorrect too. you should say "gravitational potential energy"
projectile motion graphs look like an inverted "u" (or a semi-circle)
i dont know what the "velocity" label is supposed to mean
the acceleration graph in the picture is correct ONLY if you assume that the velocity=0 or that velocity is constant

Post #502089 - Reply to (#502014) by sarah-eats-cupcakes
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11:20 pm, Oct 18 2011
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Quote from sarah-eats-cupcakes
also note that the "gravitation" label is incorrect too. you should say "gravitational potential energy"
projectile motion graphs look like an inverted "u" (or a semi-circle)
i dont know what the "velocity" label is supposed to mean
the acceleration graph in the picture is correct ONLY if you assume that the velocity=0 or that velocity is constant


Well, I understood it this way (but it was with the picture, so my interpretation might be wrong):
Gravitation -> as in what force is at work there (force of gravity would be better imo).
Velocity -> that could be simply put anywhere on the picture, it denotes v at any given moment.
Acceleration -> could be negative (deacceleration) due to friction and air resistance.


Last edited by Nidjo at 11:38 pm, Oct 18 2011

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sleepy ghost
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11:28 pm, Oct 18 2011
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Centrifugal force. No such thing exists.

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Post #502092 - Reply to (#502090) by true_grave_unit
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Quote from true_grave_unit
Centrifugal force. No such thing exists.


Errr... http://en.wikipedia.org/wiki/Centrifugal_force


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Post #502094 - Reply to (#502092) by Nidjo
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11:38 pm, Oct 18 2011
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Quote from Nidjo
Quote from true_grave_unit
Centrifugal force. No such thing exists.


Errr... http://en.wikipedia.org/wiki/Centrifugal_force

As quoted in that wikipedia article, centrifugal force is a "fictitious" force. There is no apparent cause for it. Centripetal force, sure; centrifugal force, no. I recall all of my physics teachers asserting that what people call centrifugal force, such as when you make a turn in a car, is the illusion caused by your momentum in one direction and the acceleration of the car in another direction. Ask any physics prof (simple rotational dynamics only, mind you), and they'll probably say the same thing: there is no such thing.

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Post #502095
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11:48 pm, Oct 18 2011
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I see, you're right about that. But since we use it in physics and it's on the right spot in the picture, I didn't think that way. My bad.

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Post #502103 - Reply to (#502094) by true_grave_unit
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1:32 am, Oct 19 2011
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Quote from true_grave_unit
Quote from Nidjo
Quote from true_grave_unit
Centrifugal force. No such thing exists.


Errr... http://en.wikipedia.org/wiki/Centrifugal_force

As quoted in that wikipedia article, centrifugal force is a "fictitious" force. There is no apparent cause for it. Centripetal force, sure; centrifugal force, no. I recall all of my physics teachers asserting that what people call centrifugal force, such as when you make a turn in a car, is the illusion caused by your momentum in one direction and the acceleration of the car in another direction. Ask any physics prof (simple rotational dynamics only, mind you), and they'll probably say the same thing: there is no such thing.

My thoughts exactly true_grave_unit. That was the one that stood out on my first look at the graph.

Post #502112 - Reply to (#502092) by Nidjo
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3:23 am, Oct 19 2011
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Quote from Nidjo
Quote from true_grave_unit
Centrifugal force. No such thing exists.


Errr... http://en.wikipedia.org/wiki/Centrifugal_force


http://www.physicsclassroom.com/Class/circles/U6L1d.cfm

Centrifugal force doesn't officially exist... well it does but not in the way most people think it means (it's called inertia because there is no force).
If enough people call it "centrifugal force", then that is what it's called (doesn't change the theory, only the name).

If enough people were to call a toilet 'the john', then that word would become synonymous to 'toilet'.
True, it would be easier if people would stick with the 'original' words, but this is how a language evolves (sometimes for the better, sometimes for the worse).

Last edited by Joentjuh at 3:32 am, Oct 19 2011

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Post #502131
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5:30 am, Oct 19 2011
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Yeah, I remembered some bits after true_grave_unit's explanation. I won't butt in in a discussion anymore if I can't remember something anymore. smile

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Post #502132
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5:38 am, Oct 19 2011
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I agree with centrifugal force being the mislabeled element. The force turning something to keep it moving in a curve is centripetal force.

Centrifugal force is, as was stated above, just the leftovers of the object's tangential velocity and not actually a force.

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6:00 am, Oct 19 2011
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actually, Centrifugal force does exist
the term "fictitious" is very misleading
it is the natural opposing force to centripetal
if it wasn't real then centripetal isnt real either
it originates from newton's third law of motion. the force that appears to be oppsite to the centre of the point of turn of the centripetal force is the centrifugal force, it's what happens when you drive around a roundabout. nothing is pushing you outward, but the car seat is actually pulling you inward.



Quote from sarah-eats-cupcakes
free fall is incorrect
assuming that the ball is thrown downwards from a certain height. the graph should be increasing(the gradient is acceleration) so the graph should be curve-like and going upwards until it reaches maximum height.


here's what a free fall graph should look like : (assuming that the object bounces back.if it doesnt, then just ignore everything after the point c)

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the time between C and D is the time when the object is in contact with the floor


Last edited by sarah-eats-cupcakes at 6:29 am, Oct 19 2011

Post #502212 - Reply to (#502133) by sarah-eats-cupcakes
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2:14 pm, Oct 19 2011
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Quote from sarah-eats-cupcakes
actually, Centrifugal force does exist.
...nothing is pushing you outward...

Well done.

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