Fall Definition and 921 Threads

Hello my name is Pablo, I'm new in the forum and couldn't find any similar post so i decided to ask. I have the following situation: In reference frame S (asumed stationary) there is a stick (length Lo in frame S) which falls from Yo at a vertical speed of 0.6c relative to S. In S the stick is...

Ideally I'd like to apply to graduate school for physics (leaning towards Astrophysics or Condensed matter); however, I don't think my course work or research is sufficient. I'm already using an extra year to complete the degree (I changed to physics the end of my Sophomore year) and wouldn't...

Hi there, the most basic formula from Newtonian gravitation is, for a free falling object, x = gt^2/2, where x is the displacement in the vectical direction, in the case of general relativity, this just happens to be for weak gravitational fields, for the sake of simplicity (trying to express my...

Fall internships for undergraduates? I have myself in quite the pickle. I'm entering my senior year of college pursuing a BS in Physics and a minor in Math. I go to a small university near LA. I was just offered a paid internship across the country by NASA for this upcoming fall. Of course I...

Is it because the electron has less mass and is a point object that prevents it from falling into the nucleus due to attraction of protons?

Homework Statement If I know only the circumference of the orbit of the moon, and the time it takes to make an orbit (29 days), how far does the moon fall in one second? The Attempt at a Solution I'm failing to understand how certain assumptions can be made in the geometry here. From Figure...

Generally is it as difficult to get into a PhD program in physics during the spring then it is during the fall? I'm asking because many of the schools I'm applying to say that most students are admitted during the fall but they give you the option to apply for the spring as well.

So I'm just really curious and this question is fictional, I'm new so i don't know if this is the right place to post this. Anyway, if there is 2 portal facing each other vertically and a person jump on to it, end up falling forever, i wonders how much could that person reach and is there anyway...

I applied for the SULI program for this fall and I'm really antsy to find out if I got in or not. I applied at PNNL and LANL. Has anyone heard back about their acceptance yet?

Homework Statement Assume a ping pong of mass 3g is falling, and it has fallen 1m and is now traveling at 5 m/s. If the air resistance force is half its weight, how far will it travel in the next 0.1 seconds. [Hint: you may want to sketch a velocity-time graph) Homework Equations Understanding...

Homework Statement Object A has VA =20m/s going downwards, Object B has VB=20m/s going upwards. Only gravity is given and they are traveling along a straight line vertically. What is the Δt when they meet and what Δd for object B. Homework Equations 5 Kinematic equations + v=Δd/Δt,a=Δv/Δt...

Not sure if this is a feasible schedule.for fall. Our fall semester is 14 weeks. Cal 3 (multivariable). I am taking this one with a hard professor (had her for 2 other classess/lots of work) Physics 102 (introduction to electricity and magnetism) again hard professor and I am average at...

It is a classic physics problem to calculate how long it would take to fall through a hole that passes through the center of the Earth to the other side, assuming Earth is a sphere with uniform density. I also remember being posed a problem for if you were falling through a hole that passed not...

Homework Statement Whenever I solve a free-fall problem and it asks for the time, I never am sure what the time represents once I solve for it. I understand when you throw a ball in the air and it comes back down, the time it takes to ascend up, is the same time it takes to descend down...

Hey everyone, I'm transferring into UIUC this fall, and I just registered for my classes earlier today. I'm completing dual degrees in physics and math. I've completed the introductory physics sequence, and the introductory calculus sequence, plus a 200 level introductory differential equations...

Hopefully I have this right. When they discovered the electron, they immediately realized that the electron should get sucked into the nucleus due to the electromagnetic force from the opposite charges. Why didn't they assume that the electron could orbit the nucleus to cancel out the...

According to Feynman's lecture in physics an electron doesn't fall on the proton because of the uncertainty principle. Now, if electron falls on the proton, it's position and momentum can be known so it leaves some place for it to move. But uncertainty principle is applicable for all particles...

1.An object is dropped, and falls for 4.7 seconds before hitting the ground, how high is the object when it was dropped?2. D= 1/2a[t/f][v/i][t][/i] D= 1/2a[t][/f] [T][/f]= 2D/a The Attempt at a Solution D=1/29.8*4.7 D= 23 meters

Normally in a free fall , there will be gravity acting to your body but when we free fall , we don't really feel the force , we feel weightless ( ignoring air resistance ) , ( not in contact with anything). Why?

Hi All, Can you help me, not a student (for a long time) but have a question that I need to answer. I fly drones and I'm trying to work out the following: If my 1.5kg drone fails at 400ft (122M) how long would it take to fall and hit the ground and what speed (max) would it be traveling on...

1. "An object is in "free fall" when the only force acting upon it is gravity". 2. Is gravity in this case singular or plural? Is the acting gravity the resultant force of all bodies in the universe? 3. In theory, my own bodys gravitational force is acting on the object and thus it's not...

I had a though last night that kept me awake trying to figure out what I was trying to understand. I have been out of school many years now so I have forgotten much.. Here is my question. Lets imagine there is a 30 meter diameter hole (complete with a vacuum) in my front yard that goes through...

[no template, as this post was moved from here from the Quantum Mechanics forum] In griffiths 2nd quantum mechnics, problem : Suppose I drop a rock off a cliff of height h. As if falls, I snap a million photographs, at random intervals. On each picture I measure the distance the rock has...

Problem: Find the acceleration of the blue cylindrical disk. Both, red and blue, cylinders have same mass and radius, and string is massless. Attempt: Identified three equations: one for linear acceleration of blue cylinder, and two of angular accelerations (one each for blue and red...

When you have a metallic ball hanging from a electromagnet and you disconnect the electromagnet, there is a delay between the moment you unplug the machine, and the ball starts falling. Why does this happen?

When a Vessel of water is under free fall and there is a hole in the side of the vessel, why does no water come out of the vessel? (its given in my textbook that pressure exerted on sides of vessel is zero. But what does the horizontal force have to do with the vertically acting force due to...

If an object is dropped from height, h, then gravitational energy is E = mgh, but kinetic energy when object hits the ground is E=(1/2)mv^2. Conservation of energy states that E(g)=E(k). Why does kinetic energy not depend on height object was dropped?

Background: Applied to PhD physics programs (7) , Master EE, MQF, MSMF I took a year off after undergrad, unwillingly, because I was rejected from most of the physics PhD programs I applied to. One offered an unfunded master's. I spent a lot of time figuring things out, including re-taking the...

Homework Statement In this problem I don't know the release point/origin of a dropped ball. I do however have a stroboscopic photograph of it moving through my frame of reference. In my frame of reference it moves 2.0m in 4 seconds. Now, I am suppose to figure out how far above the first...

Mostly for self interest: If I drop a 1lb weight from 15 ft (5m), what does it weigh when it hits the floor. If I have a 10lb weight and it drops from the same 5m shelf, does it weigh 10 times as much as my 1 lb weight from the 1st question? I may have the wrong terminology, but basically the...

In this case the height of the fall is far to high above Earth to be use PE=mgh. So I'm trying to integrate the inverse square gravitational force over distance. ##\int \frac{GmM_e}{r^2}dr## So I'm confused with respect to another object, specifically the moon, if the max height of the fall...

Homework Statement Equation for the time of a free fall with an initial velocity? Homework Equations √ (2 ⋅ h / a ) The Attempt at a Solution Is it √ (2 ⋅ h / via )Thanks for the help :)

Homework Statement I'm trying to show that any tunnel through the Earth (not necessarily through the center) will have a free-fall time that is the same. I heard this was true somewhere. Homework Equations acceleration of free-fall = GM / r^2 where r is changing I believe this involves trig...

Homework Statement A freely falling water drop continually evaporates. Assuming that the net momentum carried away by the vapor vanishes, calculate the velocity of the drop as a function of time. (Assume that the rate of evaporation varies as the surface area)[/B]Homework Equations dA/dr =...

why do heavier balls fall faster in liquids ?, if F=mg-drag, a heavier ball would have greater mg, but the acceleration is given by F=ma, therefore mg-drag = ma, a = (mg-drag)/m. I can't see how a heavier ball would fall faster.

Say a person was descending at constant rate of 1m/s while holding a ball. Then, without stopping, the person dropped the ball which assumed a free fall. Would the ball assume an initial velocity of 0m/s, or would it start at the one 1m/s that the person is traveling? If anyone can, please...

According to this video, a bowling ball and a feather fall at the same rate because according to Einstein, they aren't falling: https://testtube.com/dnews/which-falls-faster-a-feather-or-a-bowling-ball/?utm_source=FB&utm_medium=DNews&utm_campaign=DNewsSocial What does this mean exactly? The...

Apparent horizon recedes in front of the free falling observer, this is quite obvious. My question is, what is AROUND the observer. Spagettification stretches the observer vertically, but compresses horizontally. Do horizontal tidal forces form (apparent) white horizons around the observer?

Homework Statement My science fair project (high school sophomore) is about calculating the amount of force that is sustained from a fall off of a horse at different heights at different gaits (speeds). I would then compare the force sustained in the fall and compare it to what certified...

Hi! So i have been having this discussion with a friend. we have an old shaft going down about 100meters and we want to tie a 100kg sand bag and use it to generate electricity as it falls. (we will simply pull it back up) if my understanding is right, then: i can either generate 980kw for 1...

I've been trying to figure out this problem for hours my whole group and most of the class is stumped. We understand that we need to relate the equations of F=ma, Fd = (Cd*p*v^2*A)/2, Fnet=Fd-Fg. No data is given. The answer is a V=____ equation. Even just an answer to #1 would be very helpful...

1.If i were to jump of of Mt. Everest (29,090 ft), how long will it take me to hit the ground? The initial velocity is 0, the pull of gravity is equal to 9.81m/s^2(acceleration). I got 42 seconds, but i didnt calculate terminal velocity so I am pretty sure my answer is wrong to calculate time...

Homework Statement Estimate the time it takes a pencil of length L=10 cm to hit the ground if initially the pencil makes an angle of 0.001 rad with the vertical. Take the gravitational acceleration to be 10m/s2 Details and assumptions Assume that the pencil is just a thin solid rod with...

There is a situation that a bucket which is full of water and has a hole at the side is let to fall freely. Will the water flow out of the bucket? And if it does, will its path be parabolic or linear? Assume that there is no air and hydrodynamics is working. Full detailed answer would be...

Our test group had some issues with an ASTM foam cushion drop test, and I was asked to investigate. I fixed the problem, but noticed something in a high speed video. A 50 kg mass on the hinged platform separates from the platform when the raised end of the platform is dropped. I thought the...

Homework Statement Hello everyone, first time poster. I am in an Analytical Mechanics class and we are covering Dimensionless Form and Free Fall and am struggling with some of the concepts. The question has multiple parts, but looks like this. The equation for a damped harmonic oscillator is...

Homework Statement While standing on a bridge 18.3 m above the ground, you drop a stone from rest. When the stone has fallen 2.50 m, you throw a second stone straight down. What initial velocity must you give the second stone if they are both to reach the ground at the same instant? Take the...

Let's say that I have a stick with weight evenly distributed throughout. I attach a fan to one end of the stick, then balance it from its new centre of mass. I measure the distance from the ground to the stick then drop it. The stick tilts up towards the side generating more air resistance (fan...

In a vacuum under standard gravity, an anchored spherical metal electrode is brought to +1,000,000 volts relative to the distant walls of a much larger chamber. (I'm a new user; hopefully this will display as attachment 1) Therefore, electrons that fall through a small gap in the electrode...

Homework Statement Develop an equation that will allow you to determine the radius of the stream (r) at any distance (y) below the rim of the faucet. It would seem that the initial velocity of the water coming out of the faucet and the acceleration due to gravity have something to do with the...