Falling Definition and 1000 Threads

This is my very first post, so here it goes. I've had this idea for a while but this is my first attempt at putting it into words. We've all heard of the hypothetical demonstration that tries to put gravity into perspective by pitting a fired bullet against a simple falling bullet. The idea...

Homework Statement An asteroid is knocked out of the Kuiper belt and starts to fall toward the sun. (Assume it's initial potential energy and kinetic energy is 0.) a. Write down the differential equation for r(t) giving the position of the asteroid as a function of time. b. Solve the...

Homework Statement Problem states : A student walks off the top of the CN Tower in Toronto, which has height h and falls freely. His initial velocity is zero. The Rocketeer arrives at the scene a time of t later and dives off the top of the tower to save the student. The Rocketeer leaves the...

Hi guys! So I have been learning about jerk/jolt as the third time derivative of distance, and thinking about Newtons law of universal gravitation, and I have come to the conclusion that a falling object must have jerk, and even jounce. Here's how I came to that conclusion: The acceleration of a...

Homework Statement https://physicsforums-bernhardtmediall.netdna-ssl.com/data/attachments/72/72755-bc8e4b32405460abcfa2d8e4880f7037.jpg I'm trying to figure out the terminal velocity of the loop as it falls through the magnetic field (figure 7.20). 3. The Attempt at a Solution The...

If I were to drop a sphere down a tube of fluid. What are the effects of the wall of the tube on the sphere? Assuming the sphere has an extremely low Reynolds number of less than 1. Is it right to say that the ratio of the radius of the tube and the radius of the sphere has an effect on the...

So if you have an object in a hot air balloon that it traveling upwards at constant velocity, and this object falls out of the hot air balloon, is its initial velocity 0 or is it the same as that of the balloon? Thanks in advance!

Homework Statement A Red Cross airplane is traveling horizontally east at velocity v_0 = 80.0 m/s and height h = 350 m above the ground. The plane carries emergency supplies for a village inaccessible by road. The plane will drop the package (without a parachute) into a pile of soft hay...

Homework Statement 1. (30 points) A very flexible uniform chain of mass M and length L consisting of very small links is suspended from one end so that it hangs vertically, the lower end just touching the surface of a table. The upper end is suddenly released so that the chain falls onto the...

Homework Statement Suppose a hollow metal shell (outer radius 25.3 cm, inner radius 5.2 cm) carries charge Q = -7.99 pC. There is a tiny hole in the sphere, so small that it does not affect the charge distribution or the electric field created by the charge. An proton is released from rest at...

I had a little thought experiment, in which there are two objects with the same masses near each other (same height) on freefall. If I set up a point that is on an instant besides the two masses and call it the center of torque, I get that the torque produced by the nearest one's weight is...

You have a piano that you have just pushed to the top of the 3m long ramp that goes into the truck. The ramp is at a 20-degree angle. You think your friend has a grip on it and she think you do when you all let go. How long do you have before the piano gets to the bottom of the ramp? Assume...

Have to make a table of measurements, height-time-velocity-acceleration, taken from a free falling object and my professor asked for the acceleration of each trial which is leaving me very confused because I thought g = 9.8ms2 is constant. So I'm going to have to write a bunch of 9.8s or is...

Hey all, question about gravitational potential energy. If an object begins on ground then gains height when it falls then energy it consumes to fall down was the potential created by moving upwards, if an object was created in space, then moves gravitationally towards a celestial body where...

Consider the famous kinematics equations $$x_f=x_i+v_i\cdot t+\frac12at^2$$ My question is: does this equation work for every point A & B along the parabola formed when dropping an object?

Homework Statement The disk of mass m and radius R is at position (a), upwards. it is free to rotate round point O on it's circumference. If falls and reaches state (b), horizontal position. What are the velocities and accelerations in position (b) Homework Equations Moment of inertia of a...

I have seen youtube videos where two balls of the same size and of different masses are dropped from the same height and they hit the ground at the same time. I understand why this is so: the increase in the mass of a body increases the force of gravity acting on the body, but also decreases...

Homework Statement From what I have seen on internet sources, the average force exerted by an falling object on the ground is equal to the work done by the ground to stop the object. Assume collusion is completely inelastic and object sticks to ground after impact. F: Net force on ground m...

Homework Statement : [/B]I'm curious to know why and how one would account for the force of a falling object dropped from a height. If I apply Newton's 2nd Law, force is only dependent on acceleration. So in a straight vertical drop, this acceleration is only gravity. But is it not that a...

Homework Statement My question states that an elevator is falling on springs that are supposed to absorb the residual energy if the brakes fail to stop the elevator. They are asking how many springs are needed so that the elevator does not compress the springs by more than 0.2m? mass of...

Assuming air resistance, when a tennis ball and a feather are dropped from the same height? Which statement is true: A: Tennis ball has more mass so it will fall faster. B: Tennis ball has less surface area so it will fall faster I think the answer should be A, but the textbook say B is true...

Imagine a high cylindrical vessel (like a vertical pipe with bottom installed) of an OD = 10 inches and fluid inside that vessel (e.g. water). If we install pressure sensor on the wall of the vessel (inside the the vessel) near the bottom, it will read hydro-static pressure of the fluid column...

Homework Statement A rod of mass M and length L is in the initial position at angle θ and pivoted at the lower end. It is released and at arriving to the equilibrium state it hits elastically a mass m that slides on a surface with the friction coefficient ##\frac{\mu}{L}x## What's the angular...

Homework Statement The cable of the 2000 kg elevator cab in the figure snaps when the cab is at rest at the first floor, where the cab bottom is a distance d = 2.8 m above a spring of spring constant k = 0.30 MN/m. A safety device clamps the cab against guide rails so that a constant frictional...

I understand that the coordinate system (CS) for a distant observer Od is different than that for an observer Of who is falling radially toward the event horizon of a non-rotating black hole (BH). Using the Schwarzschild metric, I would like to understand the transformation equations that...

Homework Statement A uniform chain of length L = πR and mass M is placed on the upper half of a uniform thin disc of radius R and mass M. The disc is placed vertically and can rotate freely about its center that is fixed in space. With a small disturbance the chain starts to fall. Find out the...

Hi, Homework Statement I'm doing some research into the hydraulic jump and was wanting some help in calculating the impact force. Hydraulic jump is a phenomenon to do with the turbulence of the water - it is the 'ring' around the stream of water when a tap is turned on Homework Equations The...

Hi, I'm doing some research into the hydraulic jump and was wanting some help in calculating the impact force. The equation I have found to use is: F = m g h / s I have the mgh, and was wondering what to use as the slow down distance. If you didn't know what the hydraulic jump was, it is a...

Is it true that for a free falling observer in a non homogeneuos gravitational field, the metric according to his reference frame is always Minkowski? If it is true, Is it valid only locally?

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Dear PF Forum, I am wondering about object fall speed. Aristotle had formulated that object drops relative to their mass. But Galileo(?) suggested the other way when he dropped object with different mass (supposedly from Pisa). And astronaut had demonstrated on the moon that object regardless of...

I still don't understand this fully. Can someone please explain? I saw a video where an analogy was made, the distant observer is like an accelerating observer in flat spacetime and guy falling in is like an inertial observer, is it just like the coordinates of the distant observer from the...

Homework Statement Homework Equations I am aware that this can be done via energy methods. However, I wish to do it via: integral between t1 and t2 of Torques about point (say centre of the wheel) = change in angular momentum of the wheel. The Attempt at a Solution The torque is mgR. t1...

Hello to all ! I wanted to ask a question in this forum. I am french, and I have discussed this topic in a french physics forum, but with no clear conclusion. I hope I'll have another insights in this forum, which seems very well frequented. I know the underlying subject has been discussed in...

Hello All, I am an electrical engineer and hence quite far away from mechanics of masses. I just came to know that a spacecraft got crazy and might fall on earth. I did a simple math using MATLAB considering no atmosphere with h and m of the object as input and Nagasaki Bomb scale energy...

I am experimenting with a LiDAR system, one of my goals is to detect falling objects. The scanning frequency is 100Hz with an angular resolution of 1°. I have been able to detect an object if it is a certain size or greater moving horizontally but I'm not sure what I should focus on to make sure...

What equations can be used to compare the force of a resting X mass to the force of a smaller Y mass falling Z distance. Specifically, how much resting mass would equal the force of 300 pounds being dropped from 10 feet up?

Homework Statement Distance from planet = 10^14 meters, Radious of the planet = 10^7 meters, mass of the object = 100kg g on the planet's surface = 10 m/s^2, g 10^14 meters away from the planets center = 2.5 m/s^2 Homework Equations Fg=G*m*M/r^2 The Attempt at a Solution I calculated the...

Homework Statement A stick of length L and mass m is falling on a table with kinetic friction uK and static friction uS. Find the equation that determines whether the rod will stick or slip. If m = 10kg and L = 100cm, uS = 0.8, uK = 0.7 and initial theta = 30 degrees find the initial accel for...

Guys I know this is absurd, but it kinda makes sense to me. Recently, while i was doing housekeeping, I asked my brother to throw a piece of sponge down. He compressed the sponge and dropped it down. While the compressed sponge was falling, I saw it expanding. Seeing this, I realized that the...

If two objects of the same mass are dropped from different heights will they reach the ground at the same time

Homework Statement (Not this exactly, but it gets the idea across) I have a square loop of wire with sides L and at t=0, I have the bottom side of the loop right above a uniform magnetic field. So the flux is 0 at t=0, and right when I drop the loop, it is forced downwards at a magnitude...

Homework Statement Most physics problems that involve a falling body assume constant acceleration. How does one account for the changing acceleration if a body is dropped from a very high altitude? Homework Equations With constant acceleration, d = (1/2)at^2 or t = sqrt(2d/a) but a is not...

Homework Statement Homework Equations 1/2 mv^2 = mgh The Attempt at a Solution first, a side question, if p = mv, can't we just place p into 1/2 mv^2 so it becomes 1/2 p^2? anyway, on to the question, at the point where the cube falls off, the Fnormal should just about equal 0, correct? is...

Homework Statement A falling sphere viscometer measures the viscosity of a liquid from the terminal velocity of a tiny, falling sphere. One such device determines that a tiny sphere of radius 46 μm falls through a liquid with a terminal velocity of 2.5 mm/s. If the density of the sphere is 4171...

Sand falls on to horizontal ground at the rate of 9m^3 per minute and forms a heap in the shape of a right circular cone with vertical angle 60^{\circ}. Show that 10 seconds after the sand begins to fall, the rate at which the radius of the base of the pile is increasing is...

I am a writer, and this is the opening scene in a story I'm currently working on. A girl weighing 110 lbs gets sucked across a room, about 50 yards, then hits the wall. Her boyfriend knows that if he doesn't get her into a stasis pod within 10 minutes, she'll be dead from the massive internal...

Homework Statement An object falls freely, moving 60m in the last 2 seconds. Find the height at which it was dropped. [/B]Homework Equations Vf = 1/2(gt^2) + Vo(t)+ Yo g= 9.8m/s^2[/B]The Attempt at a Solution the object accelerates at 9.8m/s^2 . and the velocity would be 30m/s. (60 divided...

Homework Statement A stone is dropped from the top of a cliff. The splash it makes when striking the water below is heard 2.1s later. The speed of sound in air is 343 m/s. How high is the cliff? Homework Equations Δx=½at^2 t_1+t_2=2.1s t_2=x/343m/s The Attempt at a Solution I used those...

Homework Statement A stone is dropped from a bridge that is 65 m high. A second stone is thrown downwards 2 seconds later. Both the stones are heard hitting the water at the same time. The speed of sound is a constant 343 m/s. What is the initial velocity of the second stone. Homework...