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1answer
70 views

What happens if you fly a drone inside moving passenger airplane? [duplicate]

I have a little question. If I mark an X in the center of a passenger airplane, and try to fly a drone from the X mark in the moving passenger airplane (800-900 km/h), what will happen to the drone? ...
1
vote
1answer
191 views

Coriolis Effect vs airplane

So, if I build a highway from north pole towards equator and sit in a car, speed pretty fast towards it, I should feel force with the Earths rotation due to the different rotation speeds of this ...
2
votes
4answers
2k views

Riddle: can you swim faster upstream than downstream (with respect to the water)?

A friend of mine posed a riddle to me: A man swims upstream in a river, which is flowing at an unknown rate. He is wearing swimming goggles. At a certain point he loses his goggles. 10 minutes later ...
4
votes
1answer
89 views

If Speed is Relative can Absolute Acceleration be Real

This is , I suppose not a good question , but I think I am missing something which confuses me in this question. So my question is - Velocity is relative. So suppose a car is moving at a speed 200 ...
1
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3answers
71 views

Air flight and Earth's rotation

I read a response asking why flights of equal distance east and west take roughly the same time (disregarding wind actions). I have trouble visualizing part of the answer; "the speed of the rotation ...
0
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0answers
31 views

Dropping Objects on Whilst Moving Seen by an Outside Observer [closed]

As shown in the image, it seems obvious to me that the answer would be $D$. However, the answer is $C$. What is flawed in my conceptual understanding?
2
votes
2answers
53 views

How can I find the maximum height if I have changing acceleration?

I'd like to find the maximum height that a projectile reaches in motion if I have a non-constant acceleration. How would I do this? What variables do I need to know in order to calculate this? ...
1
vote
5answers
138 views

Airplane on a treadmill - Variant Thought Experiment

This thought experiment is in a way related to the (in)famous airplane on a treadmill problem. If you take a ball and place it on a treadmill, will the ball: Move backwards relative to the ground ...
4
votes
0answers
65 views

Find the relation between length of pulley and strings [closed]

A pulley is pulled with external force $F$. $x$ and $y$ denote the displacement of two ends of strings of the pulley and $z$ is the displacement of the pulley. Prove That $$z = \dfrac{x+y}{2}$$...
3
votes
1answer
7k views

What does relative to something mean?

I just started learning about vector components and relative motion. I don't understand what relative to something means. I looked online but none of the explanations are helpful. If someone could ...
12
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3answers
4k views

How to derive addition of velocities without the Lorentz transformation?

Lorentz contraction and time dilatation can be deduced without Lorentz transformation. Can you deduce also the theorem of addition of velocities $$w~=~\dfrac{u+v}{1+uv/c^2}$$ without Lorentz ...
21
votes
5answers
3k views

Is it possible to stay up while riding a bike on a moving sidewalk without actually moving?

If I ride a bicycle on a moving sidewalk so that I am not in effect moving at all relative to the ground, will I fall over?
1
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1answer
37 views

Calculating relative velocity in three dimensional space

Given two points $\mathcal{A}$ and $\mathcal{B}$ in $\mathbb{R^3}$ whose position and velocity vectors are, respectively: $$\mathbf{r_A}=\begin{pmatrix}r_{A_{x}}\\r_{A_{y}}\\r_{A_{z}}\end{pmatrix}$$ $$...
2
votes
1answer
38 views

Why does the classical Doppler formula make a distinction between movement of the source and movement of the receiver?

I've tried rewriting the Doppler formula to include only the relative velocity between the source and the receiver of sound waves. However, when I compare the results with the results of the formula ...
0
votes
0answers
61 views

Celestial bodies trajectories relative to each other and with respect to the CM

In a two bodies $A$ and $B$ system, both under the action of an internal force of interaction $\vec{F}$, the motion of $A$ as seen from $B$, is equivalent to the motion of a single body of mass $\mu=\...
0
votes
2answers
269 views

Why do objects seem to move faster (relatively) when they move tangential to the observer?

I've observed this loads of times while travelling, in cars, trains,etc.I can't quite put it in words and therefore I've roughly made a diagram to assist my question. Assume an observer is travelling ...
1
vote
3answers
789 views

How can planes land on a rotating Earth?

If the earth is rotating (e.g. at 1000km per hour, at the equator), how can planes safely land on a moving runway?
3
votes
2answers
39 views

energy of the system increasing after acceleration (one reference frame)

The system consists of small mass $m$, large mass $M$, and chemical potential energy $E_{chem}$, as shown in below image, the reference frame is following the small mass throughout. The total energy ...
1
vote
4answers
107 views

What do observers in relative motion agree on?

What are the measurements on which two observer in relative motion will agree? Other than the speed of light.
0
votes
2answers
77 views

Is polar coordinates frame non-inertial?

Consider the acceleration expressed in polar coordinates. $ \left( \ddot r - r\dot\varphi^2 \right) \hat{\mathbf r} + \left( r\ddot\varphi + 2\dot r \dot\varphi \right) \hat{\boldsymbol{\varphi}} \...
1
vote
1answer
30 views

Special Relativity and Composition Law for Velocities with respect to an observer watching two objects moving away from a central point

So I understand that special relativity is all about the frame of reference and there is a lot to do with time dilation and how space-time is warped at velocities near $c$. So my question is what ...
3
votes
1answer
247 views

Dog running after shepherd

Assume there is a dog A on a field and a sephard B. B moves on straight line with constant $...
2
votes
4answers
111 views

Ball dropped from train [closed]

A ball is dropped of a train traveling with high velocity, to a man standing near the track, the bank A) falls down vertically B) moves horizontally C) follows an elliptical path D) parabolic ...
2
votes
2answers
73 views

Why was it difficult to walk in the same direction the train's acceleration, and easier the other way around?

The other day while I was walking in the same direction that the train was accelerating. Then I came across this question. Please if would answer it, I am very curious to know. But when I walked the ...
1
vote
1answer
108 views

Objects travelling relatively to each other faster than light?

When we say that something is travelling a certain speed, it's really travelling that speed relative to the Earth. When saying the speed of anything, it is, for the most part, relative to something ...
1
vote
1answer
42 views

Kinetic Energy: Difference in energy for observers [duplicate]

Consider a stationary 10kg bike; if I apply a force of 10J then $KE=\frac{1}{2}mv^2$ so $v=\sqrt\frac{2KE}{m}=1m/s$. If we consider the same example again, but from the point of view of a stationary ...
0
votes
0answers
39 views

Relative motion on a accelerating turntable

I'm confused about a situation involving relative motion on a accelerating turntable. Suppose to have a ball bound to move in a radial track on a steady turntable. At the beginning it is moving with ...
0
votes
0answers
55 views

Doppler: how to derive formule “source moving” from formule “observer moving”

A question like this has already been asked, with a satisfying explication (the relative motion of the source and the observer with respect to the medium (air) is different), but without a derivation ...
3
votes
3answers
1k views

Einstein's first postulate implies the second?

Einstein's two postulates of special relativity are as follows, 1. The principle of relativity: The laws of physics are the same in all inertial systems. There is no way to detect absolute ...
3
votes
0answers
32 views

Disappearing galaxies [duplicate]

According to the cosmological model of the expanding universe, the distant (diametrally opposite) galaxies have bigger and bigger relative comoving speed, and this speed (which is not a relative speed ...
3
votes
3answers
142 views

Is General Relativity compatible with relative speeds bigger than $c$ between two inertial frames?

My question is motivated by a remark done by Tegmark in his book "Our Mathematical Universe". He says that GRT does not prove that relative speeds between material points are always smaller than c. It ...
2
votes
1answer
62 views

Could a gyroscope demonstrate absolute motion?

If a spaceship were moving very fast, and a rocket motor mounted perpendicular to the direction of motion/"main thruster" were turned on, the change in direction to an observer would be proportional ...
0
votes
1answer
30 views

question from the idea of relative acceleration [closed]

the accelerations of a particle as seen from two frames $S_1$ and $S_2$ have equal magnitude $4 m/s^2$ so my teacher said that the acceleration of $S_2$ with respect to $S_1$ may be anything between ...
1
vote
0answers
29 views

Direction of motion 1 [closed]

A man on a bike travelling east on straight road at 8km/h sees a car driving north at 60km/h. What is the apparent speed and diretion of motion of car to the cyclist?
0
votes
2answers
73 views

One dimensional motion - Why does a ball fall back in my hands when I throw it up in a moving bus? [duplicate]

Suppose you are moving in a bus and you throw a ball upwards. Why does it always land in your hand and does not fall behind you? The bus is moving with a uniform velocity in a straight direction. Now ...
-1
votes
1answer
42 views

While jumping in a high speed train why we fall on same place? [duplicate]

while we jump inside a high speed train why do we fall on the exact place? as train is in high speed and we are jumping so we should fall backside. but this doesn't happen why?
-3
votes
1answer
50 views

An ambiguous question on 2 balls [closed]

Two balls A & B are at rest at the bottom of a hill.Sometime after ball A is given a kick up the hill, ball B is also given a kick up the hill. When ball B is going up the hill, ball A is already ...
1
vote
1answer
36 views

Can absolute speed be determined by an object's mass?

It's been said that nobody can actually know how fast the Earth is moving through space, because a reference point is needed to determine absolute velocity. But if mass increases as speed increases, ...
1
vote
1answer
52 views

Is light relative? [duplicate]

I was wondering, if two cars (A and B) are going at different velocities let's say A=90km/h, B=80km/h then if we add the two speeds we get 170km/h meaning they are relative to each other. But if one ...
-1
votes
1answer
156 views

Relative velocity of a boat traveling on a river [closed]

I am confused about relative velocity. So suppose a boat is traveling upstream on a river and a crate is dropped overboard. The boat continues to travel upstream for 60 minutes and reaches a ...
3
votes
0answers
58 views

Faster alternative to travel to any location in the west? [closed]

Suppose one needs to travel to Somalia from Indonesia(which are approximately at a distance of $4000$ miles from each other on the line of equator). To accomplish this task, I suggest the following ...
1
vote
0answers
26 views

Force impact when lifting objects traveling at a relative velocity of 0

During a break my colleagues and I came up with the following Gedankenexperiment I would appreciate if you guys helped us find the solution for: Truck (weight 5t) traveling at 80 kph with a tow-...
2
votes
0answers
37 views

Centrifugal Force vs Motion (inertia)

Could centrifugal force be appropriately described as motion (inertia)--rather than an (imaginary) force? Could such a change of perspective eliminate much of the common confusion?
0
votes
1answer
112 views

Two Trains Relative Motion

I am confused about finding the solution to this relative motion problem: You are on a train traveling east at speed of 20 m/s with respect to the ground. Your friend is sitting on another train ...
2
votes
0answers
329 views

Portal 2 physics - one moving portal [closed]

A problem is posted and solved so many times on 9gag - till yet no good answer. The problem: you have two portals (one moving and one still standing). The one moving reach a still standing cube: what ...
0
votes
1answer
56 views

What is the effect of constant wind on a hot air balloon?

If a hot air balloon is being carried by a continuous wind current in a particular direction, in which direction will the flags on its basket wave?
1
vote
1answer
33 views

Acceleration of log moving without slipping with/under a plank

So I have this image: I know how to solve the accompanying physics problem once I have determined the relative accelerations of the logs and the plank. According to my physics textbook, the cm of ...
0
votes
1answer
235 views

How fast are we moving when standing still? [duplicate]

The Earth rotates around itself and revolves around the Sun. Our solar system revolves around the center of our galaxy and our galaxy is moving in some way throughout the universe. If you took into ...
0
votes
0answers
87 views

Simple Rotating frame of reference

I have a car moving in straight line with certain time-varying acceleration and there is another car moving in a curvilinear way along some curved path with some time-varying acceleration. The ...