Ground Definition and 921 Threads

A flowerpot is knocked off a balcony 20.0m above the sidewalk and falls toward an unsuspecting 1.75-m tall man who is standing below. How close to the sidewalk can the flowerpot fall before it is too lat for a warning shouted from the balcony to reach the man in time? Assume the man below...

Homework Statement An object is dropped from a height of 25m above the ground. What is the average velocity of the object as it falls to the ground? Homework Equations d=vit+1/2at^2 The Attempt at a Solution d=-25 a=-9.8 vi=0 -25=-4.9t^2 t=2.3s vavg=displacement/time...

Homework Statement A ball is kicked from the ground at an angle of 65° and at a speed of 8 m/s. What is its speed when it reaches 1/2 of the maximum height along the path, assuming that air resistance is negligible? My head hurts from this. I made a diagram of this event by using a...

Hi, A skydiver accelerates towards the ground at at 9.81ms ^-2. At the instant that je leaves the aeroplane. A) The skydiver opens his parachute. Explain why he reaches a terminal velocity shortly afterwards. If you could help with that question be very greatful Thanks in advance JImmer

Homework Statement To basketball player bounces the 0.60-kg basketball to another player by bouncing it off the court. The ball hits the court with a speed of 6.5 m/s at an angle of 50° from the vertical. If the ball rebounds with the same speed and angle, what was the impulse delivered to...

Homework Statement A ball is kicked at a velocity of 40.0 ms at 60 degrees above the horizontal/ a) When is the ball 25.0m above the ground? The Attempt at a Solution First i broke them down into there x and y components but having problems on the (25.0m) part. I did Vix = 40 cos 60 = 20...

Ok basically I've tried loads of methods of working it out and I'd just like to see how someone else would do it because all the answers I get don't seem right and I am not confident about them. A bit of explaining of why things that may seem odd are wouldn't be minded elther. I've tried...

1. A 10 kg box on a level surface is attached by a weightless, unstretchable rope to a 7.0 kg box which rest on a 30 degree incline. Find the rate of acceleration and the tension in the rope if... a) there is no friction ... b) coefficient of friction is 0.10 for both boxes 2. F_net...

Homework Statement What is the calculated binding energy of the electron in the ground state of (a) deuterium, (b) He^{+} and (c) Be^{+++}? Homework Equations For the hydrogen atom, E_{n} = - E_{o} / n^{2} E_{o} = me^{4} / 2hbar^2(4\piEo)^2 The Attempt at a Solution Not sure...

Homework Statement A projectile is launched from the top of a cliff with an initial velocity of 20m/s at 30deg. above the horizontal. It hits the ground 3.0s later. Given projectile range is 52m and height is 14.1m, how do i calculate it velocity(magnitude and direction) 0.1s before it hits the...

I'm confused about voltage divider circuits. I learned that the output voltage is larger than the input voltage when R1 is smaller than R2. Let's say R1=5Ohms and R2=10 and Vs=9V. Then Vo=6V! Why is the voltage lower? Did I do something wrong? (I used a voltage divider calculator, by the way.)...

[b]1. Homework Statement [/b ]http://teacher.pas.rochester.edu/phy121/PracticeExams/FinalExam/FinalExam_files/image015.jpg This is not the exact picture, instead of having M1 there let end of the string be connected to the ground instead Find the tensions and accelerations Homework...

Homework Statement At the entrance of Ambrose Channel at New York harbor, the tidal current at one time of the day has a velocity of 4.2 km/h in a direction 20 degrees south of east. Consider a ship in this current; suppose that the ship has a speed of 16 km/h relative to the water. If the...

Homework Statement Hi all - I've done all but the last part of this problem, for which I have the solution, but I was hoping someone could explain why the solution is what it is :) q:The Hamiltonian of a quantum system suddenly changes by a finite amount. Show that the wavefunction must...

Homework Statement Canadian geese migrate essentially along a north-south direction for well over a thousand kilometers in some cases, traveling at speeds up to about 100 km/h . If one such bird is flying at 100 km/h relative to the air, but there is a 30.0km/h wind blowing from west to east...

This is a 2d problem. If I drop a ball with mass m from a height L over ground. How large is the interval that the ball can possibly be on if m = 1 g and L = 2m. Use the uncertainty principle \Deltax\Deltap ~h to determine the interval. Am I supposed to think of this as a classical...

What is the principle of virtual ground? Please elaborate. Attempt: The input impedance of an op-amp is so high that virtually all input current is shunted to the feedback resistor when is works as interver. When noninverting input is grounded and internal resistance of op-amp is very high...

My college Physics class keeps on increasing my interest for physics, and I'm getting bored of the in class work so I've decided that I want to try to make a physics engine so that I can play around with physics and help myself learn more of it without being confined to just what my professor...

I mean, a book that states the basic axioms of contemporary mathematics and then proceeds to prove/derive things based on those axims. Something like a contemporary mathematics version of Euclid's Elements?

For general house wiring. As I understand it, the ground will carry away harmful power when there is a fault in the neutral let's say a wall outlet that has a load plugged into it. What keeps power from going to ground normally? Is the ground only available when a load is plugged into the...

Hi all, If I take a battery (lets assume a car battery) and connect the +ve end to Earth Ground and leave the -ve end floating. Why is there no charge transfer from the battery to ground? I've read up on a variety of threads regarding this question on this forum. Haven't quite found my...

i am now reading some materials on lanczos algorithm, one of the ten most important numerical algorithms in the 20th century my puzzle is, why it is useful for finding out the ground state energy? i can not see anything special about the ground state energy in the algorithm

0. Homework Statement What is the force required to unstick a semi sphere from the ground if the pressure inside the semi sphere is lesser than the one outside it? Assume the semi sphere has a radius of r. 1. The attempt at a solution \Delta P = \frac{F_{\text {net}}}{A} where A is...

hi there need help i just need to know why ground and neutral ( A.C CIRCUITS) short together on the body of machine chassis or panels.i found this in one oil heating unit ,with high wattage of heating element. who ever can reply ,highly appreciated with thanks

microwave can be used to engineering potentials for alkali atoms i find that in the literature, people only take the magnetic dipole transition into account why the electric dipole transition is neglected? is it forbidden?

Homework Statement A plane flies 2750 m[W] in 25s and then 5810m [S] in 67s a) What is the average speed of the plane? b) What is the average velocity of the plane? I tried doing it and I don't know if I'm right. My physics teacher can't explain anything for beans so could you please explain...

Homework Statement A bullet is fired from a cliff 36m above the ground. If the bullet is fired at an angle of 25 above the horizontal, and has a muzzle velocity of 80m/s, what is the velocity of the bullet as it hits the ground? d = 36m vi = 80m/s angle = 25 degrees Homework Equations...

Just a short question. I have five energies. -25 eV -5 eV 0 eV 5 eV 25 eV The textbook definition is that the ground state is the state with the lowest energy, i.e. I believe 0 in this case. But that is taking the absolute value of theenergies. In reality the lowest energy is...

Ok so I'm in 7th grade and I think I'm pretty good in science class. The other day we had some math questions involving some equations. One question was something like a spaceship hit the ground with a velocity of 100 m/s and then it asked like what was its mass. This question also included...

Earlier today, I just took the last examination paper for my examination in my third year in computer engineering. (One more year left to go.) Over the past year, now that I no longer have to do mathematics as a subject forced down my throat - it was a compulsory subject until the end of the...

I am having a little confusion about the difference between neutral and ground because certainly one can touch a neutral wire and never get a shock. What is neutral any way is it neutral, 0 volts. Then while handling electronics we only use DC. Now in DC there are 3 things 1.Positive(+) or...

Why a spinning top won't fall to the ground? yes I know this question must have been asked before right? tried looking for it on here but I couldn't find it.

Hi all, One of my guys was working on a control ciruit for a fan bank. The control circuit in powered by a 480-120 V control xfmr. His voltages from x1-x2 were 123 Vac. Across all energized relays: 123 Vac. But when he took voltages to ground he got around 40 Vac from the X1 bus to ground...

Hello, Non-relativistic quantum mechanics doesn't explain why the electron in the hydrogen atom (for example) "decays" from excited states to the ground state. Which theory does explain this phenomenon (from basic principles) ? Thanks.

Hey, I was looking at a car and the dealer told me the battery is at the back in the trunk. When he opened the hood he showed me how I would jump it if needed or anything else. He said there is one rod (that was visible coming through a connection from the battery) for the positive and for the...

Short Circuit Current Hi, I am reviewing a ground grid study of a substation for a wind farm that is being built. The ground grid will be for a substation with a low side of 34.5kV and two transformers that step the high side voltage up to 345kV. There are six distribution feeders on the...

Homework Statement The particle in a box model is often used to make rough estimates of ground state energies. Suppose that you have a neutron confined to a one-dimensional box of length equal say 1 x 10^-14m. What is the ground state energy of the confined neutron? answer in MeV...

I jump off a high bench (5ft high) to the ground. What is the g-force of the impact and how do you calculate it. It seems mass is irrelevant for this Joe

Hi, I am new here and have a couple questions. First, If someone is standing in their house on a carpeted floor with rubber soled shoes on and they only touch the hot wire, will they get a shock? Also, can anyone explain how those pen voltage detectors work where you only have to touch one...

Homework Statement an electron moves in 1D and is confined to the right half (x>0) potential: V(x) = -(e^2)/(8piEx) E is the permittivity of free space the ground state wave function is Nxe^(-ax) N is normalization constant, and a is another constant needed to be determined Homework...

Homework Statement I got struck with this problem again in the review questions and still can't do it, I think this problem shows a major gap in my knowledge of the subject. A solid ball of radius R is set spinning with angular speed \omega about a horizontal axis. The ball is then...

Pretty simple question that I was curious about earlier today. If I were to drop a bullet from the same height and at the same time as my friend shot the bullet from a gun, would they hit the ground at the same time? I think that they would considering the bullets frame of reference it is at...

Is the ground state of any negative potential that goes to zero at + or - infinity always even?

Homework Statement A spool of thread comprises a cylinder of radius R1 and is capped with two disks of radius R2, where R2 > R1. Some thread is tightly wound over the cylinder. The whole spool is laid stationary, side down on the ground and the thread is pulled. The spool rolls without...

Hi everyone! First post here, seems like a great community. Anyways, I'm having a bit of trouble. (I missed a bit of classes due to illness, and I'm a bit behind.) Here's the problem: You stand on top of a building 9.50 meters high, and throw a ball almost straight up. The ball is...

Homework Statement using first-order perturbation theory ,estimate the correction to the ground state energy of a hydrogenic atom due to the finite size of the nucleus, assume it's spherical nucleus. Homework Equations you can employ the fact that the electrostatic potential fi...

Homework Statement A plane is heading due east and climbing at he rate of 80kph. if its speed is 480kph and there's a wind blowing 100kph to the northeast, wha is the groundspeed of the plane Homework Equations The Attempt at a Solution w=100cos45+100sin45= 70i+70j...

How many magnetic flux quanta exist within the ground state hydrogen atom? Thanks in advance.

Hi all: As we know, if we solve the schrodinger equation, the ground state wavefunction is independent of theta and psi. We find the expectation value of ground state orbital angular momentum is zero. But if we don't do any mathematical calculation, can we conlude that? For example, Due to...