Physics help needed

[Whumbachumba]

I'm having quite a difficult time with this physics homework. We are dealing with centripetal motion, angular acceleration, angular velocity and all that. I left my book at the apartment and am not driving 45 minutes to get it. Is anybody good at physics and willing to explain this subject to me and help me with my assignment?

[ericn1300]

Originally Posted by Whumbachumba

I'm having quite a difficult time with this physics homework. We are dealing with centripetal motion, angular acceleration, angular velocity and all that. I left my book at the apartment and am not driving 45 minutes to get it. Is anybody good at physics and willing to explain this subject to me and help me with my assignment?

centripetal motion: http://www.glenbrook.k12.il.us/gbssc...ircmot/cf.html

angular acceleration and velocity: http://en.wikipedia.org/wiki/Angular_acceleration

a simple comparison of centrpetal motion and angular acceleration is to grab a beer, open it and hold it in your fully extended arm as you spin around faster and faster, watching your beer dissapear in an angular acceleration away from your centrpetal motion. and effect sometimes called centifugal force.

[Whumbachumba]

I understand the basic concepts, it's the application that I'm not getting. Here is one of my problems:

Suppose a person whose mass is m is being
held up against the wall with a constant tan-
gential velocity v greater than the minimum
necessary.
Find the magnitude of the frictional force
between the person and the wall.

1. F = (umg)+(mv^2)/R

2. F = mg/u

3. F = (mv^2)/(uR)

4. F = (mv^2)/R - (umg)

5. F = umg

6. F = mg

7. F = (umv^2)/R

8. F = (mv^2)/R

9. F = (umv^2)/R - mg

10. F = mg + (umv^2)/R

u = static friction
g = acceleration of gravity (9.8m/s^2)
R = radius
v = velocity
F = Force

Minimum velocity needed:
v = SQUARE ROOT(gR/u)

[Toksin]

You'd rather go to a bunch of clowns on a forum who most likely will intentionally mislead you for their own amusement instead of making the effort and driving to get a book that you really need for school?

Nice to see you've got your priorities straight.

[ericn1300]

Originally Posted by Toksin

You'd rather go to a bunch of clowns on a forum who most likely will intentionally mislead you for their own amusement instead of making the effort and driving to get a book that you really need for school?

Nice to see you've got your priorities straight.

Yeah, you got that right Toskin. let's see if i can screw him up even more with the beer anology.

try rephrasing the questions as:

"Suppose a beer whose mass is m is being
held up against the pull top with a constant tan-
gential velocity v greater than the minimum
necessary.
Find the magnitude of the frictional force
between the beer and the pull top."

the answer is: 2. F = mg/u

the force trying to repel the beer out of it's container is (m) the mass of the beer times (g) the acceleration of the beer divided by (u) the static friction of the the pull top holding it back. Think of your fat ass being held in by a car door keeping you from being trown out of a rapidly turning car. your fat ass is (m) your mass times (g) the angular acceleration of the turning vhecile trying to eject your fat ass divided by (u) the static friction of the door holding you in.

now try this one: A large beer keg is filled to a height h0. If the keg is punctured at a height h from the bottom of the keg, how far from the tank will the stream land (ie. where do I put my glass). Assume the top of the keg is open to air, and the cross- sectional area of the top is much larger
than that of the hole.

[2.2 Straight six]

i think what everyone's trying to say is this: quit being so damn lazy, wipe up them tears and get the damn book.

[vinnym86]

here are some of my notes that might help:

[fredjacksonsan]

Originally Posted by ericn1300

Yeah, you got that right Toskin. let's see if i can screw him up even more with the beer anology.

try rephrasing the questions as:

"Suppose a beer whose mass is m is being
held up against the pull top with a constant tan-
gential velocity v greater than the minimum
necessary.
Find the magnitude of the frictional force
between the beer and the pull top."

the answer is: 2. F = mg/u

the force trying to repel the beer out of it's container is (m) the mass of the beer times (g) the acceleration of the beer divided by (u) the static friction of the the pull top holding it back. Think of your fat ass being held in by a car door keeping you from being trown out of a rapidly turning car. your fat ass is (m) your mass times (g) the angular acceleration of the turning vhecile trying to eject your fat ass divided by (u) the static friction of the door holding you in.

now try this one: A large beer keg is filled to a height h0. If the keg is punctured at a height h from the bottom of the keg, how far from the tank will the stream land (ie. where do I put my glass). Assume the top of the keg is open to air, and the cross- sectional area of the top is much larger
than that of the hole.

You forgot to factor in the force exerted on the beer by the carbonation, and the derivative that will calculated the relative speed of release of carbon dioxide.