# Search results

1. ### DIRE NEED of HELP on HARDEST Physics Problem Ever

My class didn't get very far. I was disappointed, as I am taking AP Physics C: Mechanics, so I could not really help out as I haven't done E&M at all this year. It was pretty much up to Honors physics students who are currently studying capacitance. Anyway, I have a copy of the solution now...
2. ### DIRE NEED of HELP on HARDEST Physics Problem Ever

Ok, the seniors just gave us the answer. I may be back with another problem later, but I think this it for now. the answer was .46 rad/s
3. ### DIRE NEED of HELP on HARDEST Physics Problem Ever

http://spymaster1027.deviantart.com/art/Physics-84746563
4. ### DIRE NEED of HELP on HARDEST Physics Problem Ever

Ok, so I am in the middle of what is known as the "axe hunt" at my school. It is the culminating event of the year. The seniors puts together a scavenger hunt that is supposed to take 24 hours consisting of various clues that will require juniors to use their athletic and intellectual...
5. ### Spring SHM Problem

Homework Statement Two blocks of mass M2 and M1 (M2>M1) are connected by a spring with force constant k and are free to slide on a frictionless table. They are pulled apart and then released from rest. In terms of M1, M2, and k, what would the period of oscillation be? Homework...
6. ### Average acceleration of a ball

I am not sure if you have gotten to impulse, but if you have, then you can solve with those equations. Recall that linear momentum J equals the change in impulse - J=mv2-mv1 Also remember that J=Favg*T You'll have solved for J, and you already know that T=3 ms, so you should be able to find...
7. ### A Few Questions About SHM

I have been doing problems for the last two hours, and still haven't really gotten much further on figuring this out..
8. ### A Few Questions About SHM

I have been doing quite a few SHM problems, and I just have a few questions in general. A lot of questions evolved from one particular problem type: A mass attached to the end of a vertical spring of spring constant k. My questions: 1. How can we prove that we can use the equation...
9. ### Proof of w=(k/m)^(1/2)

So I am attempting to prove the simple harmonic motion equations with calculus so as to develop a better understanding of shm problems and have more flexibility when it comes to solving them. I am having a bit of trouble understanding the proof of w=(k/m)^(1/2) Here is how I am doing it. I...
10. ### Direction of Rolling/Sliding Friction

This much more of a general question that I've encountered in quite a few problems and I haven't found an answer to in my books or searching the net yet. Take, for example, a ball that has been propelled into motion by a spring gun on the floor. Initially, the ball accelerates so that the ball...
11. ### Graph of Kinetic Energy v. Displacement of a Falling Object

ahh.. v^2=v0^2+2a(x-x0) but since initial velocity in the y direction is 0 v^2=-2g(x-x0) and since -2g is a constant, v^2 is directly proportional to displacement, and thus kinetic energy is directly proportional to displacement! Thanks Doc Al!
12. ### Graph of Kinetic Energy v. Displacement of a Falling Object

[solved] Graph of Kinetic Energy v. Displacement of a Falling Object Homework Statement Draw and label a graph with energy for the y-axis and displacement for the x-axis of the kinetic energy and potential energy of an object in free-fall that started with a horizontal speed of 30 m/s from a...

14. ### Gravitational potential energy

[SOLVED] Gravitational potential energy edit: solved
15. ### Direction of angular acceleration

Actually, I think I get it now after messing around with some pictures..still, I think this was a stupid and poorly phrased problem.
16. ### Direction of angular acceleration

Homework Statement Imagine a car driving on the XY plane in the +y-direction. If it is slowing down, in what direction is the angular acceleration of the wheels? (a) the +x-direction (b) the -x-direction (c) the +y-direction (d) the -y-direction (e) the +z-direction Homework Equations a=αR...
17. ### Moment of inertia of a merry-go-round

ahhh, yeah, see it said a merry-go-round at a playground so I was thinking of that thing where there are just bars extending from the center and you have to hold on as it spins really fast. I don't know what it is called but I thinked that they stopped making them for safety reasons. Those...
18. ### Moment of inertia of a merry-go-round

In a certain problem I was working on, it asks for the inertia of a merry-go-round, and my first instinct was that it would be the inertia of a disk about its central axis I=(1/2)MR^2, but the solution actually uses I = MR^2 the rotational inertia of a hoop about the central axis. Why do they...
19. ### Studying Trouble Studying at Home?

deleting facebook account?? gahh..I wish I had the nerve to do that, but it would probably save like a few hours for other things each week of my life
20. ### Linear momentum bullet problem

so when I get v0/6 for part A, that is precisely what they want..if so, awesome :) then the last two parts are fairly simple
21. ### Linear momentum bullet problem

yeah, part c was for the block :) ahh..I thought I had the right answer originally but it didn't say if variables were supposed to be left in the problem, so I kind of doubted myself. Thanks for the help you guys. I am learng physixguru, maybe slowly, but learning. lol
22. ### Physical pendulum oscillation

ah! that helps a lot. Thank you so much. When I changed it to (1/12)mL^2 and used d instead it worked out great. I was forgetting about where it was rotating. Once again, thanks so much!
23. ### Physical pendulum oscillation

I just spent another 30 minutes working on the problem...and no luck :(
24. ### Physical pendulum oscillation

Homework Statement A physical pendulum consists of a meter stick that is pivoted at a small hole drilled through the stick a distance d from the 50 cm mark. The period of oscillation is 2.5 s. Find d Homework Equations T=2PI*sqrt(I/mgh) I(com)=(1/2)mL^2 parallel axis theorem...

Homework Statement A girl of mass M stands on the rim of a frictionless merry-go-round of radius R and rotational inertia I that is not moving. She throws a rock of mass m horizontally in a direction that is tangent to the outer edge of the merry-go-round. The speed of the rock, relative to...
26. ### Moment of inertia cylinder problem

Homework Statement A bucket of water of mass 20 kg is suspended by a rope wrapped around a windlass in the form of a solid cylinder 0.2 m in diameter, also of mass 20 kg. The cylinder is pivoted on a frictionless axle through its center. The bucket is released from rest at the top of a well...
27. ### Equilibrium problem involving wierd static friction

This is not necessarily a homework problem, but a sample problem of my book that I do not quite understand. A rock climber with mass m = 55 kg rests during a "chimney climb," pressing only with her shoulders and feet against the walls of a fissure of width w = 1.0 m. Her center of mass is a...
28. ### Equilibrium Ball attached to wall problem

oh, thanks!...so t*cosx-mg t*cosx=mg replace L/a for cosx t*(L/a)=mg t=mg/L*a by pyth. theorem a = sqrt(r^2+L^2) t=(mg/L)sqrt(r^2+L^2) THANK YOU SO MUCH! It feels so good to get that problem done. For awhile I thought that there would be something way complex to do that would take...
29. ### Equilibrium Ball attached to wall problem

Homework Statement A uniform sphere of mass m and radius r is held in place by a massless rope attached to a frictionless wall a distance L above the center of the sphere. Find (a) the tension in the rope and (b) the force on the sphere from the wall. Homework Equations net torque = 0...
30. ### Completely Inelastic Collision: A block and a block with a spring

re-tried it a few more times to no avail
31. ### Completely Inelastic Collision: A block and a block with a spring

I actually have two problems that I have been struggling with that are very similar, so I believe that I am making the same incorrect assumption for both problems, but I am at that point where I have been re-trying the problems for so long that I do not think I am going to find my mistake...
32. ### Gravitation/Average Force Problem

Homework Statement What are (a) the speed and (b) the period of a 220 kg satellite in an approximately circular orbit 640 km above the surface of Earth? Suppose the satellite loses mechanical energy at the average rate of 1.4x10^5 J per orbital revolution. Adopting the reasonable...
33. ### Gravitational Potential Energy Problem

a-ha! Bingo! Thank you so much. The second potential energy distance would have be the sum of the radius of the Earth AND the moon! Let's see our numbers...yep 9.8 km/s! Thank you so much!
34. ### Gravitational Potential Energy Problem

[SOLVED] Gravitational Potential Energy Problem Homework Statement Suppose that the moon were at rest at its present distance from the earth, rather than orbiting it. With what speed would it strike the earth? (Take the Earth to be infinitely massive relative to the moon) Homework...
35. ### 3-dimensional center of mass problem

Homework Statement In the ammonia (NH3) molecule, the three hydrogen (H) atoms form an equilateral triangle; the center of the triangle is 9.40x10^(-11) m from each hydrogen atom. The nitrogen (N) atom is at the apex of a pyramid, with the three hydrogen atoms forming the base. The...
36. ### Basic center of mass problem

Homework Statement What are (a) the x coordinate and (b) the y coordinate of the center of mass of the three-particle system shown in Fig. 9-22? (c) What happens to the center of mass as the mass of the topmost particle is gradually increased? Fig 9-22 shows a particle at the origin, a...
37. ### Superhard Potential energy/circular motion problem

I corrected the signs to get T1=m(g+v1^2/r) and T2=m(V2^2/R-g) I set T1 over T2 and I plugged 4gr + v2^2 in for V1^2 to get: (5g+v2^2/r)/(v2^2/r-g) I am still plugging in different values right now, but I am posting this because I think I may have the wrong expression as nothing...
38. ### Superhard Potential energy/circular motion problem

Homework Statement A ball is tied to a cord and set in rotation in a vertical circle. Prove that the tension in the cord at the lowest point exceeds the tension in the cord at the highest point by six times the weight of the ball. Homework Equations U1+K1=U2+K2 F=mv^2/r a=-V^2/r...
39. ### Gravitation and the Principle of Superposition

I'll double-check. Thanks for the help fliinghier :)
40. ### Spring and Gravity Potential Energies

so I would substitute 0 in for value to get x = .089 m, correct? Yeah, that's what I have been getting. However, my teacher told me the answer is 1.00 m. I am starting to wonder if he read off the wrong answer. Do you get .089 m too?
41. ### Spring and Gravity Potential Energies

Homework Statement A 2-kg block is dropped from a height of 0.4 m onto a spring force whose constant k is 1960 N/m. Find the maximum distance the spring will be compressed. Homework Equations U1+K1=U2+K2 The Attempt at a Solution both the initial and final kinetic energy should be...
42. ### Gravitation and the Principle of Superposition

just F=Gm1m2/D^2 I plugged in 1.5x10^11 - d1 into D^2
43. ### Newton's Law of Gravitation ratio

That is true, but I need to prove that is 1/2. The only way I can think of doing that is with a derivative. Although I do see the logic in what you are saying about taking the extreme cases.
44. ### Gravitation and the Principle of Superposition

Homework Statement How far from Earth must a space prove be along a line toward the Sun, so that that the Sun's gravitational pull on the probe balances the Earth's pull Homework Equations F=Gm1m2/d^2 The Attempt at a Solution d1=distance from probe to Earth distance from sun to...
45. ### Newton's Law of Gravitation ratio

Homework Statement A mass M is split into two parts, m and M - m, which are then separated by a certain distance. What ratio m/M maximizes the magnitude of the gravitational force between the parts? Homework Equations F=Gm1m2/d^2 The Attempt at a Solution I first just tried plugging...
46. ### Forces Problem Involving A Tree Branch acting as a monkey's pulley

Ah! Thank you, I was thinking about that but with regard to mg. I was changing mg to be positive or negative and was getting an acceleration of 2 m/s^2 Once again, thanks! :P
47. ### Forces Problem Involving A Tree Branch acting as a monkey's pulley

Homework Statement A 10 kg monkey climbs up a massless rope that runs over a frictionless tree limb and back down to a 15 kg package on the ground. (a) What is the magnitude of the least acceleration the monkey must have if it is to lift the package off the ground? If, after the package has...
48. ### Tranlastion Motion

Homework Statement A red train traveling at 72 km/h and a green train traveling at 144 km/h are headed toward one another along a straight, level track. When they are 950 km apart, each engineer sees the other's train and applies the brakes. The brakes decelerate each train at the rate of...
49. ### Struggling with post-lab question

5. A block of wood floats in a beaker of water. According to Archimedes’ principle, the block experiences an upward buoyant force. If the beaker with the water and floating block were weighed, would the measured weight be less than the sum of the weights of the individual components? Explain...
50. ### Weightless physics question

I have a problem asking me what velocity must be achieved so that a person on at the top of a ferris wheel with a 15-m diameter can feel weightless. I am wondering how you define weightless. At first I tried setting mg=0, but I couldn't get anywhere that way.