# Search results

1. ### Simple Compression question

What am I doing wrong in this problem? You need to record an entire collection of your favorite music. It consists of 39 hours of music. Assuming you are using MP3 encoding (MPEG Audio Level III at about 128kb per second), how many CDs will you need? (hint: a CD can store up to 700 MB of...
2. ### HELP! Harmonic Motion

Can you offer some help on the following question? I've been trying different things for a while but can't get the right answer. Thanks! At time t = 0, consider a 1/2 wavelength long section of the rope which is carrying the wave y = 0.06 cos(2.1 t - 2.4 x) between two points which have zero...
3. ### Radius of Gyration? REALLY

Radius of Gyration? REALLY need help ASAP! Hey - If any of you can help me with the following problem asap that would be awesome! A racquet consists of uniform lamina that occupies the region inside the right-hand loop of r^2 = cos 2theta on the end of a handle (assumed to be of...
4. ### HELP! Angular Acceleration

Okay... treating them as point masses: alpha = torque / I = (m1)gr - (m2)gr / m1(r^2) + m2(r^2) = 12(9.8)(0.25) - 6(9.8)(0.25) / ((.25^2) (m1 + m2)) = 13.1 Is that right? So the position of the center of mass doesn't really matter in this case? Thanks!
5. ### HELP! Angular Acceleration

A dumbbell consists of a slender rod of negligible mass and small spheres attached to each end with mass 12-kg and 6-kg respectively. It is pivoted at its center about a fixed horizontal frictionless axle and initially held in place horizontally. The length of the rod is 50 centimeters and...
6. ### If there is a net torque on a system does that mean there's net force on the system

if there is a net torque on a system does that mean there must be a net force on the system

Suppose now that I want to calculate the tangential force. I set torque = I(alpha) = F(R) F = I(alpha) / R = (1/3)ML^2*(a/R) / R F = (1/3)ML^2*((g sin_theta)/(L/2)) / (L/2) I got that F_tangential = 4/3Mgsin_theta, but they got that the answer is 1/4 Mg sin_theta. What did I do...

thanks Everything did come together. Thank you for your help!

Mechanics...PLEASE HELP VERY SOON! Can someone please help me with this problem? I've been working on it for hours - anything would help thanks! A system consists of a uniform stick of length L and mass M hinged at one end. The hinge is released from rest at an angle theta_0 with respect to...

11. ### Rotational Motion

would the smaller inertia hoop be going faster or does it not matter? I think we did this experiment where we found acceleration to be g sin theta / (1 + c), where c was the constant of inertia. (i.e., 1/2 for a cylinder and 1 for a hoop).
12. ### Rotational Motion

I'm a lil confused: so by conservation of energy I have: mgh = 1/2mv^2 + 1/2Iw^2 mgh = 1/2mv^2 + 1/2I(v^2/r^2) V^2(1/2m + 1/2(I/R^2) = mgh v^2 = mgh / (1/2m + 1/2(I/R^2)) For spoke one, the mass is greater, so speed decreases... But wouldn't I be smaller? Wouldn't that increase...
13. ### Rotational Motion

re; The part of I'm confused on is this: The wheel with the spokes has more mass, which increases inertia and decreases speed. But it also has more mass concentrated around the radius, which increases speed...
14. ### Rotational Motion

Two hoops of identical radii roll without slipping down identical inclined planes under the influence of gravity. Hoop 1 is identical to Hoop 2 except for some massive spokes which are fixed to the rim. If the two hoops are released at the same time from the same height, which hoop makes it...
15. ### Simple momentum problems

Hey, just want to double check on these: Rain falls vertically into an open boxcar coasting freely on a horizontal frictionless track. As a result the momentum of the system consisting of the boxcar plus accumulated water increases. - I said true - since there is no friction, velocity...
16. ### Elastic collision

A cart of mass M and a second cart of mass 2M collide head on elastically and bounce apart. Which cart experiences a larger magnitude of acceleration during the collision?
17. ### Magnitude of Total Momentum

Say there was 2 collisions. There are 2 carts of identical mass. In the first case cart A starts at height h above the ground and crashes into cart B which is stationary on the flat ground. They stick together. In the second case, cart A starts at height h/2 above the ground, cart B starts at...
18. ### HELP! Block up incline

There's a block of mass M that's pulled up an incline by a force T. The block starts from rest and is pulled a distance L by the force T. The incline, which is frictionless, makes an angle (a) with respect to the horizontal. 1) Write down the work done by force T. That would just be W =...
19. ### HELP! mechanics problems

Thanks for your help! I just need one more clarification. So I understand that external forces are not the same as conservative forces, so then it's FALSE to state that if the work is done by conservative forces, then momentum is conserved?
20. ### HELP! mechanics problems

Hey, can any of you clarify a few things for me? I'd greatly appreciate it, thanks! If the work done on an object is by conservative forces, does that mean the momentum is conserved? I know if there aren't any external forces, then momentum is conserved. Does conservative forces mean no...
21. ### Really simple problem - can't get right answer!

Suppose a 50kg block slides along a horizontal surface where the coefficient of kinetic friction between the block and the surface is uk = 0.60. A force F = 400 N is now applied, where the angle of the force above horizontal is 20°. What is the magnitude of the acceleration of the...
22. ### Circular Motion -

Circular Motion - please help ASAP! Two identical blocks are tied together with a string and placed along the same radius of a turntable that is spinning about its center. The inner block is 4 cm from the center and the outer block is 6 cm from the center. The coefficient of static friction...

and... thanks doc, but I still don't see how I can eliminate Vob...
24. ### Lines and Planes in Space - HELP SOON!

oh nm oh nevermind... that was a stupid question. I see it now. Got any suggestions on the other problems? :)
25. ### Lines and Planes in Space - HELP SOON!

okay, so it's <-9. -6. 12> Does it make a difference though?
26. ### Lines and Planes in Space - HELP SOON!

I am very confused regarding a few problems in Calculus III. Any help or hints to any of these would be greatly appreciated! 1.) Are lines L1 and L2 parallel? L1: (x-7)/6 = (y+5)/4 = -(z-9)/8; L2: -(x-11)/9 = -(y-7)/6 = (z-13)/12; The answer says that they are parallel, which I...