Speed Definition and 999 Threads

Homework Statement This is a problem from the Cambridge Natural Science Admissions Assesment. A student carries out an experiment to measure the speed of sound. A loudspeaker that emits sound in all directions is placed between two buildings that are 128 m apart as shown. The student and...

Hi all. I am not a mechanical engineer but I've been working on an idea which consists of a linear shaft with Reciprocating motion. Since the device only works with rather a high speed shaft, I wanted to know what are the speed restrictions of a linear shaft? So let's give it some numbers. The...

Homework Statement An object of mass m=2 kg slides down on a track from a height of h = 10 m. The track is frictionless except the horizontal range between the points A and B. The friction force is constant between A and B. What is the speed of the object at point B if the magnitude of the...

Homework Statement They stated in the problem that the radius is 6.3. Why did they multiply it by 10^3 during the calculation? Homework Equations It's in part 1 and 3. The Attempt at a Solution [/B]

Homework Statement Three freight cars of equal mass are coupled together. The freight cars are traveling at 6.7m/s down a straight track when they collide with two more stationary identical cars. If all five cars are coupled together after the collision, then what is their speed if they are on...

is anyone looking for what might be the effect of something going into or coming out of the speed of light?

What will happen if something traveling faster than light is found?What effect will it have on modern physics?

I recall reading on this forum that a theorem had been proved to the effect that is there was a effective speed limit c in SR then there would only be one such limit for all relevant phenomena. Is this true and if so can you point me at it as I don't seem to be able to formulate the question...

GW170817 showed that gamma rays came 2 seconds after gravitational waves. (after 130M years) Are these two seconds uncertainty at determination of difference of these speeds? Or is it possible to explain, why 2 seconds of difference, or is it possible to explain, at least, a part of this...

Suppose at the instant a gravitational wave passes through an interferometer, one of the interferometer's arm get stretched by 1%. Would the wavelength of the photon traveling in the arm also get stretched by 1%? If so, then would the frequency of the photon remain the same and hence increasing...

Homework Statement The question wants us to find the velocity that the car can take without assistance from friction. The friction, in this case, is the normal friction, weight friction, and the static friction (pointing towards the right). I understand how it got ncos(15) - w = 0 for the y...

Let's say there are two objects. One is thrown directly downward at v0 and the other is thrown horizontally (90 degrees) at v0, both from height h. Which object will have a higher speed by the time they hit the ground? Would they have the same speed? For the object thrown downward... h = (vf2 -...

Homework Statement Two cars are 1.4 km apart and driving towards each other. One car starts from rest and accelerates uniformly at 1.2 m/s^2. The other car is driving at a constant speed of 18 m/s. When will the cars meet? Homework Equations d=vt d=ut + 1/2at^2 d=vt-1/2at^2 v^2 = u^2 + 2ad...

Homework Statement A 0.14-km wide river flows with a uniform speed of 4.0 m/s toward the east. It takes 20 s for a boat to cross the river to a point directly north of its departure point on the south bank. What is the speed of the boat relative to the water? I'm mostly concerned about the...

Homework Statement A mass hangs from a light string of length 45cm attached at its other end to the ceiling. If the mass is given an initial speed of 5m/s, what is its speed when it reaches point A in its circular path (see Figure 1)? https://imgur.com/a/ERdlD Homework Equations ##E_i = E_f##...

Hi all, I've been lurking around the forums for a while to get help with homework but I figured I'd finally make an account to get direct feedback. I'm having problems with this centripetal acceleration problem, Homework Statement "In an old-fashioned amusement park ride, passengers stand...

Homework Statement Maxine (mass m) slides down an icy slope then along a flat surface before coming to a stop. The slope has angle θ and height h. a. Derive a formula for speed at the bottom of the hill in terms of the angle of the hill θ, the height from which she starts h, and the...

Homework Statement A boat, moving at the velocity of 9,9m/s turns off its engine and starts decelerating at the rate of a=-kv^2. What is the velocity of the boat after 4,9 seconds if the constant k is k=5,5m Homework EquationsThe Attempt at a Solution I tried to integrate deceleration to get...

Hi! I am confused with the speed regulation for Isochronous control. In Droop control, we can surely solve for a value of speed regulation because droop allows the generator to have a varying frequency. However, in Isochronous control, the frequency and speed from no-load to full-load is the...

Help with the question of the concept of the stability of the speed of light. I gather that current atomic clocks are based upon the speed of the electron around their nucleus, which is a function of the speed of light. Measurements of the speed of light that depend upon atomic clocks therefore...

Question: The speed of waves in shallow water depends only on the acceleration due to gravity (g) and the water depth (h). Which of the following formulas describes the speed of the wave? a) (1/2)gh^2 b) gh c) h/g d)(gh)^(1/2) Attempt: Change in V = at t= ΔV/a Δx=vt+(1/2)at2 Δx =...

This is a thought experiment so the mentioned values are only for example purpose. I was wondering about an electrical train. So here is the setup, we have rails and an electric train with an overhead wire. In one case the train gets its power from DC and in the other case the train is powered...

Hi! I have this homework problem that has me completely stumped. Any help is greatly appreciated! In coming to a stop, a car leaves skid marks 80m long on the highway. Assuming a deceleration of 7.00m/s2, estimate the speed of the car just before braking. I just can't figure out what formula...

[FONT=verdana]Dear Everybody, I need some help to help the distance for part a. b) If the block comes back down after it was push, what is the speed back down. A 3.25 [FONT=verdana]kg block starts with a speed of[FONT=verdana] 15 m/s at the bottom of a plane inclined at...

1. We have a moving platform traveling 700 miles per hour to the Right-Direction. 2. In the middle of the platform, we have a gun which fires a laser both at the front and back of the platform at the same time. 3. We have at both the front and back of the platform, a mechanical device. These...

Homework Statement A parallel-plate capacitor is charged to 4850 V. A proton is fired into the center of the capacitor at a speed of v0=2.81 * 10^5 m/s. The proton is deflected while inside the capacitor, and the plates are long enough that the proton will hit one of them before emerging from...

Homework Statement A Van de Graaff generator is one of the original particle accelerators and can be used to accelerate charged particles like protons or electrons. You may have seen it used to make human hair stand on end or produce large sparks. One application of the Van de Graaff generator...

When replying to this thread: https://www.physicsforums.com/threads/the-nasa-zero-gravity-flight.927136/ I became uncertain of my understanding of the physics after the plane starts to descend. What I imagine happens is that your forward velocity would remain constant and you would be...

Plane A flies from Paris to New York, while plane B makes the same trip via London. Assume that the total time taken for both planes is the same. Considering the two trips, both planes have the same average velocities but different average speeds. Why? How is this possible?

Homework Statement An electron is fired from x = 0 with an unknown V0 at 45 degs to the horizontal between two parallel plates separated by 2 cm. Electric field is 103 j N/C. Find: a) The max value of V0 so that the electrons don’t hit the upper plate 3.75 * 106 m/sHomework Equations If you...

Homework Statement (Problem #1 on this page.)[/B] Homework Equations ##v=\sqrt { \frac { T }{ \mu } } =\lambda f## The Attempt at a Solution I don't think there is enough information, ##v=\sqrt { \frac { Mg }{ m/L } } ## m, the mass of the string is not given

Homework Statement 2. Homework Equations Similar triangles The Attempt at a Solution $$\frac{y}{30}=\frac{50}{x}~\rightarrow~x=\frac{1500}{y}$$ $$\frac{dx}{dt}=-\frac{1500}{y^2}$$ $$s=16t^2=16\frac{1}{4}=4$$ $$\frac{dx}{dt}=-\frac{1500}{16}$$ The answer should be ##~\displaystyle...

Homework Statement 13.30 The colar B slides along a guide rod that has the shape of the spiral R = bθ. A pin on the collar slides in the slotted arm OC. If the speed of the collar is constant at v0, determine the angular speed ##\dot θ## of the arm OC in terms of v0, b, and θ. Homework...

I am a fourth year biomedical and mechanical engineering student and my final project has to do with designing a crash test dummy. The end goal is to mount the dummy on a bicycle and launch it at ~20kh/h, then it will be struck by an automobile driving at ~30km/h. Various different impact...

Homework Statement I didn't get it. Consider velocity space. The no. of velocity vectors for a given speed is proportional to the surface area of a sphere of radius v in the velocity space. So, a fraction of velocity vectors with speed v in an elemental area dA is##\frac{ dA}A##. A = ##\Omega...

Homework Statement The sprinter completes 200m in 19.3sec. When the starting pistol fires he accelerates constantly until he reaches his top speed of 13.4m/s. He then holds speed till the 200m point. At what time did he stop accelerating and how many meters did he cover before reaching top...

Dear all, In a recent talk, I have heard that speed of gravitational waves is non-dispersive. How is it proved "observationally" in LIGO detections that all the frequencies travel with the same speed, so one can say the speed is non-dispersive?

1. Homework Statement A whirlygig is made by hanging a mass, m1 = 386.0 g, through a tube and then spinning another mass, m2 = 198.0 g around so that it forms a circle. When this happens the string makes a small angle with the horizontal as shown in the diagram. If this is done at a specific...

For my IB Physics Extended Essay, I have just changed my topic from momentum to this and I have really little time of doing it... (Due in Oct) :cry::cry::cry::cry::cry::cry: My research question would be The effect of angular velocity of circular motion of a moving sound source on the sound...

Homework Statement A mass of m = 1.40 kg is placed on a 2.00 m ramp. The angle of the ramp can be adjusted by changing the height of the top of the ramp. In reality there is a small amount of friction between the block and the ramp: μs = 0.261, μk = 0.119. If the ramp (with friction acting)...

Object A starts from the origin velocity 3 m/s and object B starts from the same place with the velocity 5 m/s, 6 seconds later. When will B Catch up with A?

i was wondering if anyone had a site that catalogued windspeed effect on heavy objects? I found several sites that talk about trees and shingles, I'm interested in flower pots and deck boxes. If someone could shoot me an equation would allow me to calculate various objects

A parachutist is falling with speed 176 ft/s when his parachute opens. If the air resistance is Wv2/225 lb where W is the total weight of the man and the parachute and v is in ft/s, find his speed as a function of time after the parachute opens.

If we have a circle rotating then a force v^2/r is produced but no net directional force exists as it cancels. But if the wheel was not uniform in mass ie not rotating around its centre of mass AND the speed changes over time as a function of the "wheel"'s rotation angle could a net force be...

0 down vote favorite There is a lot of material discussing the rotational speed of the magnetic disk in HDD but not about the rotational speed of actuator arm. What are the typical actuation speeds of the actuator in HDD? This information will be used in the design of a fast shutter system...

Net Neutrality is being overturned as ISP telecoms claim they need to throttle bandwidth and speed as too many customers want to stream HD videos and play HD online games. EM waves are fast and unlimited, so is Tiered Premium Billing absurd? ISP telecom expenses include transmitters...

Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level? I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...

Why does an increased electrical permittivity reduce the phase velocity of light in a medium? Furthermore, what interactions do we see on an atomic level? I am aware of the equation that defines the speed of light in terms of the electrical permittivity and magnetic permeability, but I do not...

Imagine yourself to be bat. You can't see anything. You don't have eyes. All you can do is echolocate, using ultrasound. Now imagine something is moving away from you faster than the speed of sound. Can you locate it ? Can you perceive its existence ? If the answer is yes, how ? If no , then...

First, let me apologize if I don't give you enough info. If I'm missing something, please let me know and I'll try to get the info. Here is the set up: Car A is traveling West at 5 mph. Car B is traveling South at X mph. Car B strikes A on the rear quarter panel (centered on the rear tire)...