# Search results

1. ### Archived Transformation of Gravitational to Kinetic Energy

I am not following the template for the reason that this is a generic question. Consider that the change in kinetic energy is 1J. Suppose further you have two particles, both of equal mass that are gravitationally attracted to each other (and the change in energy comes from the fact that they...
2. ### Center (in y direction) of Mass of 3D pyramid

Got it got it got it! 3.6 is constant. Brb [EDIT] Works. You made me think of it. I was looking at integrating from the top and wrote out eqn to reverse and realized... wait a minute, i'm scaling the width but its constant... TYVM.
3. ### Center (in y direction) of Mass of 3D pyramid

That shouldn't matter. Take the center of mass from 7.85m from the top. Interestingly. 7.85m is the middle of the triangle.
4. ### Center (in y direction) of Mass of 3D pyramid

Homework Statement A monument is made from stone blocks of density 3800kg/m^3. The monument is 15.7m high, 64.8m wide at the base, and 3.6m thick from front th back. How much work was required to build the monument? (Hint: find ycm). Homework Equations ycm = (1/M) * ∫ydm, M = mass total...

Thank you!
6. ### Moments - How are they actually calculated?

Moments -- How are they actually calculated? Hello, I have a question. Is the moment calculated: Force times the distance or Force's perpendicular component (to axis) times the distance. For example, lets say I have a stick. Pulling on it is not moment. So if I push at the...
7. ### Physics of a TreadWheel [Abstract Concept?]

Yeah, I figured that after I thought about it a lot. So F = ma, and we have the tangental force at the radius of the bigger circle. But f = ma, and once again, we don't have m and we shouldn't even have a. The circle should not be accelerating. The angular velocity anyway.
8. ### Physics of a TreadWheel [Abstract Concept?]

Homework Statement [EDIT] Cleaned up the problem. A tread wheel crane is an ancient device used to lift heavy objects. It consists of a large circle (like a hamster wheel) for a person to walk inside. The large circle connects to the middle where there is a small circle that is attached a rope...
9. ### Challenge Problem

Homework Statement A person standing at the top of a hemispherical rock of radius R kicks a ball (initially at rest on the top of the rock) to give it a horizontal velocity v. What is the minimum initial speed to ensure the ball doesn't touch the rock? Homework Equations x^2 + y^2 = r^2...
10. ### Error Propogation

Ugh... I'm just a first year. My statistics class is next year and I only have to follow standard rules for now, so even if I wanted to, I probably shouldn't look up formulas, especially when there are apparently more than one way to do something (as per yourself). Also, why should one thing...
11. ### Error Propogation

This isn't a homework problem. I'm just having ALOT of trouble understanding how to do error propogation. [EDIT] These are actually lab results. But its not a "homework" question. Its how to do uncertainty. Just trying to be clear. Consider we take different measurements of an objects...
12. ### Structural Engineering Stress Question

Ah, I appreciate it. I got it, thanks a lot.
13. ### Structural Engineering Stress Question

Aha! Thank you... that clarified a lot. Okay, I have another really difficult question: again, this is problem set so please push in the right direction. A mercedes-Benz weighing 4000kg and travelling 160km/h runs into a concrete post. Assuming all kinetic energy is used to crush the low allow...
14. ### Structural Engineering Stress Question

Interesting... Sure, my solution was really close, but only because I appeared to have picked a good diameter. I could easily have picked a bad diameter and got it wrong. So what was fundamentally wrong with my solution? Also, I notice that one cannot solve for the area (diameter) or the...
15. ### Structural Engineering Stress Question

Wait... whaa...? How can you not assume any diameter..? What is going on here...what formula is that. Isn't the length you can go down heavily dependent on the diameter of the piano wire? That formula doesn't assume anything. You could lower a 0.1cm diameter wire or a 1m wire... But if you...
16. ### Structural Engineering Stress Question

Homework Statement Piano wire weighs 77kN/m^3 and breaks at a stress of 3000MPa. Calculate the length of piano wire that can be lowered down a very deep mine before it breaks. Homework Equations stress = force/area The Attempt at a Solution Piano wire = 77 000N/m^3 stress = 3000...
17. ### How To Incorporate Sensor Uncertainties With Multiple Measurements?

Ah, so a systematic error cannot be reduced. I appreciate it a lot. I left out information of the experiment but it was irrelevant.
18. ### How To Incorporate Sensor Uncertainties With Multiple Measurements?

That uncertainty comes from variance of the data. But it does not incorporate the fact that the data points themselves have imprecision. Does it?
19. ### How To Incorporate Sensor Uncertainties With Multiple Measurements?

Lets say a sensor measures within accuracy of +/- 0.05N And you take multiple measurements and graph it out. (I.e., 5.12N, 5.15N, 5.05N...). What is the uncertainty of the final average? One way I read is: Sx = s/√N where s = std. dev. N = number of data points But...
20. ### Rigorous Uncertainty Analysis

So what about the original problem then? 255.53 ± 11.3?
21. ### Rigorous Uncertainty Analysis

A position of a particle in linear motion is given by: x = vt + 0.5at2 Calculate x with the error for: t = 25.3 ± 0.5s v = 10.1 ± 0.4m/s a = 2.5 ± 0.3m/s2 So for calculating vt: q = (10.1) (25.3) = 255.53 (exact) Δq = (10.1)(25.3) * √ (0.4/10.1)2 (0.5/25.3)2 = 11.31... Therefore, vt =...
22. ### Static Equilibrium Two Pulleys and Weights With Ring

No... this is a force diagram and the angles are clearly different. At least according to this scale diagram [EDIT] Oh my god your right... Thank you!
23. ### Static Equilibrium Two Pulleys and Weights With Ring

I have a problem. Lets say there were two pulleys put at equal height. You have a metal ring and attach three wires to it. At the end of each wire, have three weights of mass w. One weight hangs down, one weight goes over one pulley and the other over the other pulley. The system goes to...
24. ### Newton's Third Law of a car and truck

Ah yes. That was silly of me. Fell in a common trap (and thing is, I've heard this before). Are you implying that given perfect collision, the force on the truck would NOT be 500N and instead must be calculated based on conservation of momentum? mv = mv You know the car's velocity and...
25. ### Newton's Third Law of a car and truck

This is perfect for the question I am stuck on. I am just a first year so this may be stupid but... You are assuming that the car accelerates at the same rate as the truck. I think that is wrong in its own way but more to the conceptual point, let me write up a new example: Assume there is...
26. ### Newton's Third Law of a car and truck

I have a question for which I am intensely confused. Lets say a car was pushing a big truck from behind. And the car (and truck) are accelerating, then there is a breakdown because the car applies all the force it has to the truck, which pushes back with equal force. So the car shouldn't be...
27. ### Rubens Tube - Finding a One Inch Reducer and PTC

This is probably very late but I hope you get to see it. I had 4 tough exams and a lot of summatives due. I thank you so very much for this post, and I appreciate all the help. I am in the process of looking at them and will let you know (if you care) how it goes.
28. ### (Very Basic) Movement of Charged Particles Through Parallel Plate Apparatus

Homework Statement What is the electric potential two-fifths of the way through a parallel-plate apparatus (from the positive plate) if the plates have a total separation of 5cm and field strength of 5000N/C. Homework Equations Difference Potential Energy = Electric Field Strength x Distance...
29. ### How Does the Electric Energy formula Depict Energy Between a Positive and Negative?

This is probably a silly question. The Electrical energy formula is this: Ee = k(q1)(q2)/r So lets say a positive and negative charge are directly next to each other. Conceptually, there should be no potential energy there. But the formula (r=0.00001m) suggests that it is huge. On...
30. ### Rubens Tube - Finding a One Inch Reducer and PTC

Hello and thanks! I apologize in advance if I picked the wrong place to post this thread. I'm a high school student building a Rubens tube and have encountered a problem: I have a one inch outside diameter aluminum tube. It turns out that the one inch copper reducer and PTC I bought is...