Fall Definition and 921 Threads

Seen it argued that in Monty Fall - the same setup but the host trips and accidentally reveals a door with a goat - does not have the same odds. I disagree. A) your initial chance of picking the correct door is 1/3 B) the odds are 2/3 one of the other doors has the car should then not matter...

v1=460m/s×2, v2=0 m1=m2=5kg R=6378km a1=460m×460m/s/s/6378/km/1000/m×km=0.13m/s/s a2=0 F1=m1×a1=0.66kg×m/s/s F2=m2×a2=0 G=9.81m/s/s F3=(m1+m2)×G=98.1kg×m/s/s (F3-F1)/10/kg = 9.744m/s/s Where the heck did I go wrong?

1. So for an asymptotically far-away observer, something falling towards a black hole will never reach it 2. However, the thing falling in will reach the event horizon is finite affine parameter 3. The Universe has a finite age for an asymptotically far away observer a) Does this mean that one...

I was wondering do strong wind slow down or has any effect on the outcome of your free fall? Like slower down your impact or help you survive? Hypothetical, you free fall down height of 1,000 feet below are just rocks so hard surface (not water). Basically it should cause death. But let say...

I'm stack at the very beginning. If I use Newton's second law to find acceleration and integrate until I find the position, I must face $$v(t) = \int_0^t g-\frac{\lambda v}{m} dt'=gt-\frac{\lambda }{m} \int_0^t\frac{\partial z}{\partial t}dt$$ But this last term feels pretty weird. I don't...

Homework Statement: I have a 80 foot tree weighing 4000 pounds ready to fall on my cabin. How thick of a cable or a nylon rope a do I need to stop it from hitting the cabin? Homework Equations: m=f/g I am 82 years old and can no longer do the math on this real problem I have due to a brain...

A particle was resting on top of a dome and given a negligible push such that it falls. The question is at what angle will the particle fall off the dome. The solution is that, m\frac{v^2}{a} = mg\cos\theta - R and by conservation of energy 0 + mga = \frac{1}{2}mv^2 + mga\cos\theta then the...

This is my wrong attempt, the bolt's equation for ##t\geq 2## would be ##y_b(t)=-\frac{1}{2}g(t-2)^2+e(2)+l## where ##e(t)=\frac{1}{2}wt^2## the position of the elevator's floor in the absolute frame of reference. ##d(t)=-\frac{1}{2}(w+g)t^2+2gt+2(w-g)+l## the distance between the bolt and the...

My current understanding is that a person falling toward the surface of a planet with no atmosphere, would feel no force acting upon themselves even though they are accelerating relative to the planet. If the mass of the planet suddenly tripled while the person is in free fall, would the person...

Why air resistance has less force than gravitation force in free fall? If Egg is fall from a nest of tree, while falling, it has less magnitude of air resistance than gravitation force. Where net force is not equal to zero.

I am wondering if an object can fall into a black hole at faster that the speed of light. I have heard that the expansion of the universe can make distant galaxies appear to recede from one another at velocities faster than the speed of light.

 Intuitively, this makes sense to me. I am...

Let's say we have a wire and a circuit is closed the magnetic field start to spread with speed of light c. Then we would have a place " out of range " at which the magnetic field doesn't exist.What is the equation that connects magnetic force with distance with its prorogation of speed of light...

Hello, I have a problem to understand acceleration in GR, objects in free fall move along a geodesic, they are in inertial motion. But observer on Earth can clearly see that falling thing accelerates. What causes the acceleration, when there is no gravititional force? Thanks for answers.

Homework Statement A 0.1 kg nut is thrown by a squirrel off of the top of a 10 m tall tree. It is thrown with an initial upward velocity of 4 m/s and an initial horizontal velocity of 3 m/s. a) How long till it reaches the top of its arc? b) From the top of its arc how long till it reaches the...

Just read somewhere that we have left some 500,000 pieces of debris orbiting around earth. Some probably are near enough to touch a little atmosphere so it is reasonable to expect they will fall eventually. But what about the ones a little further? Will they never return to earth?

Homework Statement Not an actual homework problem but a discussion that came up in class while we were learning about torque. A tall box is sliding across a surface with friction f, mass m, and velocity v. What equations would you use to figure out if the box would tip over while sliding to a...

Hi! I was wondering about an object free-falling to Earth (or wherever) in a vacuum from a very high altitude where g is significantly lower than on the surface: let's say 5,000 km for instance, where g would be 3.08 m/s2 according to the equation gheight = gsurface · (RadiusEarth / (RadiusEarth...

Is there an easy way to explain this to a 3 year old?

Homework Statement A 200 kg object moves at 10 m/s at 20m (vertically). It falls to a height of 5 m. Find the new speed. Homework Equations vf²=vi²+2ad The Attempt at a Solution vf²=(10m/s)²+2(9.8m/s²)(15m) vf=19.8m/s To find the distance for the new speed I did 20-5, but I'm not sure it's...

Homework Statement This question is actually two question. We have two hollow frames - one is rectangular and another is triangular. the rectangle is rotated and fixated such that the angles in shape are ##\alpha , \beta = 90 - \alpha## and the angle of triangle is ##\alpha##. We have two balls...

Homework Statement A 2.0 kg object starting at rest falls 3.0 m onto a 4.0 N/m spring. How far will the spring be compressed? m = 2.0 kg vo = 0 m/s2 y = 3 m k = 4 N/m g = -9/8 m/s2 Homework Equations eq1: Fg = mg eq2: Fspring = -kx The Attempt at a Solution [/B] eq1: Fg = mg Fg =...

Homework Statement Why does a longer stick fall over slower when pushed? So for example, you have a 3-meter stick and a 1-meter stick. You hold them so they run from the floor toward the ceiling. You let go of each stick and they fall as a tree would. Why does the longer stick fall slower than...

So, I've been reading a whole bunch of different answers to this online. Some people say yes, some people say no. I'm totally confused...

Homework Statement A flat cushion of mass m is released from rest at the corner of the roof of a building, at height h. A wind blowing along the side of the building exerts a constant horizontal force of magnitude F on the cushion as it drops as shown in the figure below. The air exerts no...

Homework Statement A ball is thrown upward with a speed v 1. The ball reaches a maximum height of y=h. What is the ratio of the speed of the ball,v 2 , at y=h/2, to the initial upward speed of the ball,v 1 , at y=0? Homework Equations I attached a picture. We are currently studying the four...

Problem: https://drive.google.com/open?id=19PDuyshgP6u4U9mXU3BfrF031J8wL12B Attempt: I tried to solve the range by listing out the Newton's 2nd laws of each drum https://drive.google.com/open?id=1Eslg2Wy3orG41eywwm_O6qN4OQ3QN-bA and from the equations of the drum 2, I get...

Homework Statement "A falling object travels one-fourth of its total distance in the last second of its fall. From what height was it dropped?" Reference: Up is (+) Scenario 1 (Complete motion) a = -9.8 v1 = 0 d = -x v2 = ? Scenario 2 (Motion at the last second) a = -9.8 d' = (1/4)(-x) t' =...

In Classical GR the metric tensor ##g_{\mu\nu}## determines the length of rods and ticking of clocks while the connection ##\Gamma^{\alpha}_{\mu\nu}## determine the equation of geodesic (the free fall motion of particle). Furthermore, in GR the Levi-Civita connection is uniquely determined by...

I was doing some conceptual problems quickly before moving on to the numerical stuff when I glanced at this answer given in the solutions manual, and it surprised me: Which object has greater speed at the bottom of its fall, object A of mass m dropped freely from height h or object B of mass m...

Hello, Let us imagine a solid in a free fall on planet Earth and let us neglect the effect of air resistance on the motion of the solid. According to Newton's Second Law of Motion, since the only force being applied on the solid is its Weight, then its acceleration must be its Weight divided by...

This thread is for the SULI internship for Fall 2018. The application deadline was May 30th and offers are given until around August 7th. Has anyone had any luck getting accepted to a lab? What labs did you apply to? When did you apply and how long did it take to receive an offer?

As I understand it, Newton considered the influence of gravity between two objects to be instantaneous. Now it would appear that gravity has a speed limit. If the Earth is influenced by the sun from where it was 8 minutes ago, how does the Earth keep up with a traveling sun? Does relativity...

I've decided to return to my local community college this coming fall. I'm going to major in Physics with a concentration/intention to go into engineering with it. There aren't that many information technology/computer science/entry level helpdesk job postings where I live. On Indeed.com...

Homework Statement which one would be faster when reached the ground? Homework EquationsThe Attempt at a Solution conservation of energy Pe=Ke mgh=1/2mV^2 for 2-)m*g*cosa*(h/cosa)=1/2*m*V^2 -- V= sqrt(2*g*h) for 1-) V=sqrt(2*g*h) so V1=V2

Homework Statement A satellite of mass m_s orbits the Earth in a circular orbit of radius r_0. If the satellite orbits at the upper part of the atmosphere and the friction force f is constant, it would trace an spiral and fall to the earth. but if we suppouse that the friction force is small...

Bridge fall paradox Another thread urges me to think of stress in materials in TOR and let me make a "paradox" to think of it as follows. --------------- A train is running on a bridge over a wide river. Evil terrorists switch on the bombs set on legs of the bridge to crash whole the bridge...

For many, many years (don't ask), I've been running into the classic example of the local reference frame: the man in the box who can't tell if he's floating free in space, or falling into a gravity well. It occurs to me that if one is in a falling box, a mass released at the top of the box...

In a soccer match Putu kicked the ball with the elevation angle \alpha so that it reached the maximum height 10 m. How long must he wait until the ball fall to the ground if g = 10m/s^2? I don't know how to do it if the initial velocity isn't known. Can someone help me?

Homework Statement We release m_o = 1 kg object from h=1m height. How much does the Earth move (x)? I just need the comfirmation if I did correctly? Homework Equations Conservation of momentum: m_o v_o + m_E v_E = 0 The Attempt at a Solution I wrote the energy conservation law as (beginning...

Homework Statement A body is falling from a height of 720m. Divide this distance into three parts so that the body would overcome all parts in the same time. P.S (This is translated from a different language) Homework Equations x(t)= x0+V0+at2/2 v(t)=V0+atThe Attempt at a Solution I made an...

<Moderator's note: Moved from a technical forum and thus no template.> An object with mass 96 kg is given an initial downward velocity −3m/s in a medium that exerts a resistive force with magnitude proportional to the square of the speed. The resistance is 60 N when the velocity is −2m/s. Use...

The equations of a falling object dropped from a 1000 foot tall building are simple: eq 1 ##s=1/2( at^2)## eq 2 ##v(final)=(2as)^.5## eq 3 ##v(final)=at## where a is the acceleration due to gravity at the surface of the earth s is the height of the building, t is the time it...

Let`s observe fall down of an long elastic vertically placed rod which has two point A and B. Point A is being placed on the ground and not moving, Point B is being free. We observe that the free ending is bending backwards and gets an arc shaped form. In your option, is it an optical...

Today, I had a thought experiment where I began to puzzle over inertia of very large masses being dropped. Imagine a scenario where the Moon was suspended 100 m from the surface of the Earth alongside a marble at the same height. Now ignoring air resistance and the gravity exerted by the Moon...

I am currently applying to grad school and have submitted all of my applications. None of my applications have my fall grades, just my schedule. I took 3 graduate courses (the only ones I've ever taken). I got an A in 2 of them, however I withdrew from the last one because I was too busy this...

Hello, so i know in a free fall the acceleration is constant (9.8 m/s2) therefore speed/velocity is increasing.. But I am wondering why we can't use Speed=D/T

So I was on my way to school this morning and looking at the beach made me think of something. Why doesn’t the water on Earth fall out and into space? Like, if you really didn’t think too hard, you’d be like, yeah, the Earth is tilted, so why, doesn’t the water fall out like a glass of water? If...

It will be very helpful if someone suggest any articles or reading materials on this topic for detailed study.

This is something I haven't been able to wrap my head around yet. In physics, I've always been told that gravity is a force that ALWAYS works between "objects" with mass. Now, it seems clear to me that if a feather and a hammer were to be dropped at the same time on Earth (without air...

Hello. Sorry for my English... I have made some calculations. By Iterative calculation. With Excel. The time that need two objects to fall from 10 meters to 2 meters. The mass of the objects i choose are: 1 and 10 kilos. 2 and 10 kilos 5 and 10 kilos. And. 1 and 9 kilos 3 and 7 kilos. 5 and 5...