Falling Definition and 1000 Threads

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?

edguy99 submitted a new PF Insights post https://www.physicsforums.com/insights/quantum-animations-stop-electron-falling-proton/ https://www.physicsforums.com/insights/wp-content/uploads/2015/05/quantumanimations-80x80.png...

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...

I have been thinking about a simple thought experiment in classical electromagnetism that seems to disobey conservation of energy. I'd be very interested to hear where people think I'm going wrong. Imagine that we have two oppositely charged objects with charges +q, -q and masses m. Assume...

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...

On youtube, I came across to one of many videos trying to explain General Relativity. One of the comments was interesting to me: "I understand how gravity causes an object with velocity to go in curves or to orbit, due to the curvature of space-time: the object thinks that it's traveling in a...

Sometimes when I'm lying on my back, trying to fall asleep, I create an image of something very small like a floating dust particle, marble, pinpoint, or a tiny steel ball. My brain automatically imagines an extreme weight or massive density of the tiny items. Then suddenly, a very odd feeling...

Homework Statement A chain of mass M and length l is suspended vertically with its lowest end touching a scale. The chain is released and falls onto the scale. What is the reading of the scale when a length of chain, x, has fallen? (Neglect the size of individual links.) Homework Equations...

Homework Statement You will learn a lot about the motion of falling objects in chapter two. At this time you do not have to make any measurements. This exercise is purely numerical. The following table shows the position of a falling apple, in meters, at several instants in time. The clock was...

Homework Statement A rod of mass ##M## and length ##l## is pivoted at the center(##O##) in horizontal position. An object of equal mass(having velocity ##v##) falls vertically on the rod at distance ##\frac{l}{4}## from ##O## and sticks to it. Find the angular velocity of the rod just after...

Homework Statement A uniform chain of length L and [constant] mass per unit length λ is suspended at one A end by an inextensible light string. The other end of the chain B is held at rest at level of end A of the chain. [See image.] Now if the end B of the chain is released under gravity...

Homework Statement A rope of mass M and length l lies on a friction less table, with a short portion, ##l_0## hanging through a hole. Initially the rope is at rest. a. Find a general solution for x(t), the length of rope through the hole. (Ans: ##x=Ae^{\gamma t}+Be^{-\gamma t}##, where...

it is said that a settelite is a free falling body. For free falling body its velocity should free continuesly increasing. Is it true? I am confused..

A cup with a mass/weight at the bottom was filled with cotton and an egg was place inside for a physics project. As the cup was falling, it would always re position itself to fall with the bottom/heavier half first (the bottom contains the mass). Would it make sense to explain this case this...

Homework Statement A uniform ladder having mass 14kg and length 3m is released from rest when it is in the vertical position. If it is allowed to fall freely, determine the angle Theta at which the bottom end A starts to lift off the ground. For calculation assume the ladder is a slender rod...

Homework Statement A 250 g object is dropped from a height of 150 m. What is the kinetic energy after falling to 100m Homework Equations V2^2 = V1^2 +2ad Ek = 1/2 mv^2 The Attempt at a Solution I used the kinematics equation to find my v2 then I used this to find Ek. I got the answer 120J but...

why water become thinner when falling? thanks guys.

1. A parachutist of mass 62 kg is falling at 55 km/h when her parachute open. She then falls 24 m in the next 2.0 seconds. Find the force of air resistance acting on the parachute during those 2.0 seconds.2. Could I just find the force of friction?3. I found out what the force would be if not...

Homework Statement A solid spherical ball is placed carefully on the edge of a table in the position shown in the figure. The coefficient of static friction between the ball and the edge of the table is 0.5 . It is then given a very slight push. It begins to fall off the table. Find the angle...

1.Small ball with mass m falls from hight h. Find how velocity, acceleration and height depend on time. Air resistance is linear and depends on velocity ##F = kv##. 2. Air resistance ##F=kv## where ##k## is constant. 3. I do not know where to go after ##ma = mg - kv ##.