piper210_355

yeah that is the coefficient of static friction. ok so i read on a website that static friction=mass*coefficient of friction which would be F(k)= 2.5*.19 F(k)=.475 How can I find out what the normal force is? And how do I know what the radius is when the problem only tells me that the penny is 10cm from the center? Do I just use 10 as the diameter?

okay so i'm assuming the I is inertia which is found using (1/2)mr^2 so I= (1/2) (1.9) (.05)^2 I= .002375 but before i can put this in the equation you gave me i need to find out what the angular velocity is. What equation can I use for that? I looked on the internet and found one that said i could divide the angle by time but the equation doesn't give me time.

i looked online and some of the equations that i found are: Force=mass*centripital acceleration centripital acceleration= velocity squared/radius

I need some help w/ this prob: A solid disk of mass 1.9kg and radius .05m rolls w/o slipping along a horizontal surface w/ a translational speed of .240 m/s. It comes to an incline that makes a 35 degree angle with the horizontal surface. Neglecting energy losses due to friction, to what height above the horizontal surface does the disk rise on the incline? So the problem gives me the following variables: mass:1.9kg r:.05m v:.240m/s angle:35degrees I'm not sure how to proceed though. What equation(s) should I use?

I need help determining whether or not a penny will stay on spinning disk (neglecting air resistance) given these variables: mass of penny: 2.5g distance from center: 10.0cm static friction: 0.19 angular velocity: 33.3rpm speed: 45.0rpm I'm not sure what equation(s) i should use so if you could tell me that would be a great help.

ok so i did the conversions I don't know what equation to use for the angular speed though. I'm currently working on finding the radius when the angular speed is the same, but i'm not sure how to do that either Merged post follows: Consecutive posts mergedi saw in one site that the equation for angular speed is v/r=w Merged post follows: Consecutive posts mergedok so with that equation it think I can do your exercise questions: at the begining r=45 so w= (123)/45=2.73 in the end there is no tape on the reel so r=12 and w=123/12=10.25 Merged post follows: Consecutive posts mergedso what do i do to find out when the radius is the same?

I need help with this problem. My teacher gave it to us but I'm not sure how to proceed. The tape in a standard VHS cassette has a otal length of 246m, which lasts for 2.0 hr. As it starts the full reel has a 45mm outer radius and a 12 mm inner radius. At some point during the play both reals have the same angular speed. Calculate the angular speen in rads/sec and in revs/min. Hint: Between the two reels the tape moves at a constant speed My teacher said we might find these equations helpful: W=R/R(f) W is angular velocity V=L/t πr^2=.5(πR^2-πr^2) I know I have to convert 2.0 hr to 7200 secs. If I use the second equation she gave then I get V= 246/2=123 I know how to convert rads/sec to revs/min, I just don't know where to start with the problem.

ok so i'm going to put what i did just to make sure i understood/did it right tan 24.23=F(n) .45=F(n) F(n)F(k)=F(?what exactly am i calculating here?) (.45)(.28)=F(?) .126=F(?) F(p)-F(?)=F 10.05-.126=F 9.92=F a=F/m a=9.92/2.5 a=3.97m/s^2 I hope that's right thank you sooooooooooo much for your help

ok so i substituted it in for F(y): F(a)cos70=F(a)(sin70)(.253)+(.8)(9.8) .34F(a)=.238F(a)+7.84 .102F(a)=7.84 F(a)=76.86 Then I used this to find the value of F(x) since that's the normal force. F(x)=F(a)sin70 F(x)=(76.86)(sin 70) F(x)= 72.22 Thank you sooooo much for your help I'm sorry it took so long I would have never been able to do these probs w/o your help

:DYES:D Ok I got the rest of these steps from a video on youtube, but I just want to make sure it's right. First it said to get the force of gravity: F(g)=(gravity)(mass) F(g)=(9.81)(2.5) F(g)=24.5N Then I found the Force of the parallel (that's what they called the line in between F(n) and F(g) in the video). F(p)= F(g)sin(24.23) F(p)=(24.5)(sin 24.23) F(p)= 10.05 After that I used newton's second law to find the acceleration. a=F/m a=(10.05)/2.5 a=4.02m/s^2

ok so what i did was that i took the sin 70 which if i'm not mistaken should equal F(x). sin 70=F(x) .94=F(x) Then I put this in the equation for frictional force that you gave me earlier. F(f)=uF(x) F(f)=(.253)(.94) F(f)=.238 After that I put it in to the equation you gave for F(y). F(y)=weight of sponge + F(f) F(y)=(.8)+(.238) F(y)=1.048 My plan is to do the pythagorian therum to find the applied force, but I want to make sure i am doing it right so far.

actually on my paper it looks like this would it be the same thing?

ok so I rearranged and I got this: tan(theta)=F(x)/F(n) tan(theta)=F(f)/[F(f)/u)] Here is where I'm not sure if i'm over simplifying(since in the other one i am dividing by a fraction i then change it by multipling by the reciprical) tan(theta)=F(f)*[u/F(f)] This cancels out the F(f) leaving... tan(theta)=u so then (theta)=tan^(-1) .45 (theta)=24.23 is that right? I really hope it is(I think it is). I'm pretty sure i know how to find the acceleration from here. All i need to know is if the angle is right.

ok so would the normal force still be mass times gravity in this problem or no.

would it be the static friction since in this case the force of gravity = static friction

ok so i calculated the sin(20)=.342 and the cos(20)=.940

ok so i looked at the graphic and in terms of tan though tan(theta)=F(x)/F(normal)

so F(gravity)=F(normal)+F(parallel) ? Or should it be something else...probably since you said theta had to be in there. so is R another way to denote normal force? I'm sorry this is taking so long I'm scrambling all over the place trying to find some stuff that can help me with these physics problems, since the teacher didn't

wouldn't i find F(f) by using the equation from earlier? In order to do this i need to find the normal force. Can i somehow use the angle (maybe by using sin or cos) to get the normal force and i was thinking wouldn't the applied force and the normal force equal the same thing? If so then i only have to look for one and i'll have both.

ok so in this case gravity=static friction I'm thinking to find force normal i use F(s)=F(normal)u(s) F(normal)=F(s)/u(s) F(normal)= 9.81/.45 F(normal)= 21.8 am i ok so far?

so if i break it up into components would it be F= F(normal)+F(frictional)+weight of sponge ??? I think i'm starting to get it a little bit more but I'm still a bit confused

i have a picture drawn, but how does this help me find theta?

I'm guessing that one of the equations is the F(friction)=uF(normal). In another problem that I did, the normal force was mass x gravity (although I'm not sure if i can do that for this prob since it is vertical). If i can do this then it would be F(f)=(.253)[(.800)(9.81)] F(f)=1.98 Would this be the magnitude of the normal force or am I way off? I'll do some more research to try to find an equation that will help me find the magnitude of the Force applied.

i'm thinking that maybe i can some how use the friction that is given to find the angle. is that right?

that make sense. i did it again with (x+2) and got 4.20. Thank you sooooooo much for your help.