# 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

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...
3. ### 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...
4. ### 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...
5. ### 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...
6. ### 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...
7. ### 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...
8. ### 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...
9. ### 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 =...
10. ### 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...
11. ### 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...
12. ### (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...
13. ### 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...
14. ### 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...
15. ### How Can A High-Torque Motor Have Low a low RPM

Torque is the rotational force. If there is more force, how can the motor be slow? I'm building a DC motor and read that given a constant amount of coil, creating a very dense coil will increase torque but lower RPMs. Conversely, making it looser (bigger radius) increases RPM but lowers torque.
16. ### Ruben's Tube - Is a one inch OD pipe okay?

Hello everyone! I'm in high school and attempting to build a ruben's tube. I am on a very strict budget and came across free brass tubing, but the diameter is 1 inch. All the tutorials I've seen use a diameter of at least 2inches if not more. Will a pipe with a one inch diameter work...
17. ### Grade 12 2-D Wave Interference

Hello and thank you! I am having trouble understanding Mr. Thomas Young's equations for the double-slit apparatus with the bands etc. Specifically, for constructive interference: Length = PS1-PS2 = n(lamda) What I understand is that this n value is the phase shift in their wavelength...
18. ### Lenz's Law of Electromotives

The Law: The direction of the induced current creates an induced magnetic field that opposes the motion of the inducing magnetic field. Application: When the north pole of a magnet goes INTO a solenoid, the opening where the magnet is entering from becomes South. As it exits, the same opening...
19. ### What is Lenz's Law of Electromotive Forces and How Does It Work?

I'm in grade 12 physics trying to understand how motors work. My teacher is useless. I read the official law, but I do not understand how it conceptually works. Here is the aplet he gave me, if you want to explain with respect to a visual...
20. ### Extremely Hard Conservation of Momentum Problem

Homework Statement A 0.750kg block of wood is attatched to a spring with k = 300N/m. A 0.0030kg bullet is fired into the block, and the spring is compressed 0.102m. Calculate the velocity of the bullet before the collision. Is this elastic or inelastic? Homework Equations How do you do...
21. ### Finding the Spring Constant of a mattress

Homework Statement A mattress manufacturer estimates that 20 springs are required to comfortable support a 100kg person. When supporting the person, the 20 springs are compressed 0.035m. Calculate the spring constant for one sprint. Homework Equations The answer is 1400N/M at the back of...
22. ### Conservation of Momentum v.s. Conservation of Energy

Hi, I'm new to this forum. So I do not understand how, in an inelastic system, momentum is conserved. Consider this problem: Tarzan swings from a branch 4 meters up and picks up jane how far can he swing up the other side? He weighs 100kg and is standing still on the branch. He jumps...