The relative-motion tag has no wiki summary.
0
votes
0answers
10 views
1D Kinematics - Relative Motion involving non-inertial frames of reference
I recently came across a question involving non-inertial frames of reference. I didn't quite understand the way it had been solved due to some conceptual confusion regarding certain deductions made to ...
0
votes
1answer
40 views
Relative Velocity problem
I was solving many problems on relative velocity and observed that when the question asks,
"what is the minimum time taken by the boat/man to cross the river.?"
so the solution says that he ...
0
votes
2answers
74 views
What is our estimated running speed on Moon's surface?
I was wondering if we have the chance to run on the Moon's surface, how would you expect it look like?
I expect our velocity will increase for the same work we do on Earth, but not sure if this will ...
2
votes
1answer
101 views
Is there a closed form solution to the Esdale river problem?
This is probably not well known problem but it looks like open problem. What kind of methods there are to find a closed form solution to the physical situation?
Can you solve this problem?
You're ...
-4
votes
3answers
179 views
There must be free positive charges, moving oppositely to electrons for the wire with current to stay neutral
All popular expositions (e.g. these ones) of relativistic electromagnetism claim univocally that electrons in motion become more dense due to the speed. They teach that Lorentz contraction of charges ...
-1
votes
1answer
57 views
man walking in rain:relative velocity
A man walking in rain at a speed of 3kmph find rain to be falling vertically. When he increases his speed to 6 kmph, he finds rain meeting him at an angle of 45 deg to the vertical. What is the speed ...
2
votes
2answers
72 views
Distance versus drop
Why if the earth is spinning at 1000mph a person falls from 10 stories his body didn't land about 1.4 miles away but right down as if the earth didn't spin at all
0
votes
6answers
180 views
Inertial Frames of Reference - Inertial vs. Accelerated Frames
According to Robert Resnick's book "Introduction to Special Relativity", a line states the following as the definition of an inertial frame of reference: "We define an inertial system as a frame of ...
2
votes
2answers
74 views
Reality error and relative velocity
Suppose a person is walking in rain carrying an umbrella. He is tilting his umbrella at some angle with the vertical so as to protect himself from the rain. But a neutral observer who is standing ...
3
votes
1answer
105 views
Does a fly get brought up to speed with a bus?
Consider a scenario where a bus is moving at a constant speed and a fly enters through a window,the fly is also flying at a constant speed.
Since the bus is not in contact with the fly and neither is ...
4
votes
3answers
333 views
A fly in an accelerating car
A fly is flying around in a car, the fly never touches any surface in the car only fly’s around in the air inside the car. The car accelerates. does the fly slam in to the rear window. or does the fly ...
2
votes
1answer
103 views
Is there a stationary frame of reference?
My understanding of relativity is at the beginner level, so please bear with me to help a beginner to understand. Something which I don't understand is consider if you travel close to the speed of ...
5
votes
2answers
232 views
Earth moves how much under my feet when I jump?
If I'm standing at the equator, jump, and land 1 second later, the
Earth does NOT move 1000mph (or .28 miles per second) relative to me,
since my velocity while jumping is also 1000mph.
However, ...
-1
votes
2answers
170 views
Simple Vector Problem [closed]
I'm a bit stuck on a homework question that I've been assigned. The question is as follows:
You are paddling a canoe at a speed of 4 km/h directly across a river that flows at 3 km/h. (a) What is ...
1
vote
0answers
23 views
Rolling (without slipping) ball on a moving surface 2 [duplicate]
Possible Duplicate:
Rolling (without slipping) ball on a moving surface
Apparently I didn't log in properly when I asked a question this morning: Rolling (without slipping) ball on a moving ...
2
votes
1answer
296 views
Rolling (without slipping) ball on a moving surface
I've been looking at examples of a ball rolling without slipping down an inclined surface. What happens if the incline angle changes as the ball is rolling?
More precisely I've been trying to find ...
7
votes
5answers
440 views
How can kinetic energy be proportional to the square of velocity, when velocity is relative?
Let's start with kinetic energy (from los Wikipedias)
The kinetic energy of an object is the energy which it possesses due to its motion. It is defined as the work needed to accelerate a body of a ...
1
vote
2answers
118 views
Moon and the moving train
While travelling by train (travelling West to East), it seems the moon is moving in opposite direction when seen from the window, but then it reverses its direction, after a certain amount of time and ...
1
vote
0answers
70 views
What direction a flag on an object moving in the wind shows?
"The flag of a ship that is moving northward with 10 km/h, points exactly southwestward. The windsock at the lighthouse points under 30 relative to the western direction southward. Calculate the ...
2
votes
1answer
125 views
Galilean relativity in projectile motion
Consider a reference frame $S^'$ moving in the initial direction of motion of a projectile launched at time, $t=0$. In the frame $S$ the projectile motion is:
$$x=u(cos\theta)t$$
...
2
votes
2answers
288 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 ...
3
votes
5answers
324 views
Measure absolute speed
Currently I'm 17 years old, going to secondary school. So, my ideas might be totally wrong...
I know that everything is relative. In the example of speed, the earth moves, and the galaxy moves, etc.
...
1
vote
1answer
82 views
Waves travelling with water flow
Suppose I use a tool to create a circular wave in the river. If there are two fish swimming 1m from the source (2m from one another), they will both feel the wave at the same time.
What will happen ...
1
vote
1answer
309 views
Calculating velocities using Reference frames
Suppose an object A is traveling at a velocity of 100 m/s, and another object B is traveling at 105 m/s. With both the objects traveling through the same direction, taking A as a reference frame, the ...
0
votes
1answer
111 views
Galileo's dictum and how light cannot violate it
Okay. So I've been told that the speed of light is constant and cannot violate Galileo's dictum, but even if it weren't constant (in a vacuum), how would it violate it anyway?
Say you are on a train ...
2
votes
4answers
188 views
Space Expansion vs. Relative Motion
Inspired by a recent dialogue from another question:
Given 2 objects moving at some velocity $v$ relative to one another, is it possible to determine whether they are moving or whether the space ...
1
vote
1answer
211 views
Relative Speed vs speed of light [duplicate]
Possible Duplicate:
Travelling faster than the speed of light
Someting almost faster than light traveling on something else almost faster than light
I've got two questions which are ...
-1
votes
1answer
59 views
Molecules motion in the moving frame, made it as a non inertial frame [closed]
Since according to relativity moving frame is equivalent to rest frame ... physical laws hold on in the both frame in the same way. Now imagine a isolated jet which moves at sonic velocity .. jet is ...
0
votes
2answers
385 views
Does an airplane's speed include the speed of the Earth?
After take off, does airplane's speed include Earth's movement/speed? Do airplanes turn with Earth movement/rotation?
0
votes
1answer
171 views
Bee in a vehicle [duplicate]
Possible Duplicate:
Speed of a fly inside a car
Just a conceptual question: If a flying bee is inside a speeding vehicle, will it have to "fly" just as fast as the vehicle to stay aloft ...
3
votes
2answers
880 views
How to deduce the theorem of addition of velocities?
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 ...
0
votes
1answer
125 views
What would happen to electronic circuits when traveling near the speed of light?
Imagine a space ship, loaded with all sorts of computer systems, traveling near the speed of light.
Electricity itself is very fast, and can reach speeds close the speed of light. (up to 99% ...
4
votes
3answers
771 views
Is acceleration relative?
A while back in my Dynamics & Relativity lectures my lecturer mentioned that an object need not be accelerating relative to anything - he said it makes sense for an object to just be accelerating. ...
0
votes
1answer
132 views
In What Frame of Reference does the Special Theory of Relativity Operate? [duplicate]
Possible Duplicate:
Time Dilation - How does it know which Frame of Reference to age slower?
This has bugged me for years.
According to the theory of relativity, the faster an object ...
0
votes
4answers
452 views
How does a train, airplane measure its speed?
I always get the doubt about this. I know that a bike measures its speed based on the motion of its front wheel. So what is the case with train? Is it same principle? Then what about an airplane? Is ...
0
votes
2answers
466 views
What will be the relative speed of the fly? [duplicate]
It has happened many times and i have ignored it everytime.
Yesterday it happened again .
I was travelling in a train and saw a fly (insect) flying near my seat.
Train was running at a speed of ...
4
votes
1answer
290 views
Lorentz force law in Newtonian relativity
I know that in special relativity Electric and Magnetic fields mix together in different reference frames, but my question is about classical mechanics.
It seems weird to me is that the Lorentz Force ...
1
vote
3answers
340 views
Does being suspended in air allow you to not be affected by Earth's rotation?
Let's assume that there was some mechanism by which we could remain suspended in air. By this I mean that our feet is not in contact with the ground. One possible way of doing this would be by means ...
2
votes
1answer
286 views
Einstein Relative Motion and Time Order of Events
According to Einstein, do observers in relative motion agree on the time order of all events?
I don't think they would agree on the timing of events, but I am having trouble figuring out why they ...
2
votes
4answers
395 views
How is this classical “paradox” resolved in electromagnetism?
A magnet and a coil move relative to each other. In the frame of reference of the magnet, there is a magnetic field and consequently a force acting on the charges in the coil according to the Lorentz ...
2
votes
2answers
484 views
Galilean transformation in relativity
Assume flat spacetime in a general relativistic framework (or special relativity for that matter) and two observers $A$ and $B$, with non-vanishing velocity relative to each other. We know that they ...
2
votes
3answers
4k views
Will a ball thrown straight up in a train land in same spot (in real world)?
I have a question that came up in a discussion with friends. If I throw a ball straight up in an enclosed train car moving with constant velocity, I believe the basic physics books say it will land ...
3
votes
1answer
127 views
Equation of Motion in a Non-Inertial (Rotating) Frame
Let me preface my question by informing you this is for an assignment, so I would rather not have explicit answers but rather be given guidance in arriving at the correct solution.
The question is ...
5
votes
2answers
196 views
Why absoluteness of time implies galilean transformations?
In Landau course, vol.1 Mechanics, one finds the statement: "...the absoluteness of time necessarily implies that the ordinary law of composition of velocities is applicable to all phenomena."
I ...
29
votes
8answers
9k views
Why does the atmosphere rotate along with the earth?
I was reading somewhere about a really cheap way of travelling: using balloons to get ourselves away from the surface of the earth. The idea held that because the earth rotates, we should be able to ...
2
votes
4answers
220 views
Chosing a reference frame in which the earth is at rest and doesn't rotate
We may choose a non-rotating earth as our reference frame and ask ourselves: how about the planetary and stellar motions. A star at a distance of 10 million light years would turn around the earth in ...
