Questions tagged [relative-motion]
Use this tag for questions related to how objects move relative to other objects dependent on your frame of reference, and how this applies to special relativity.
698
questions
0
votes
1
answer
44
views
Does the rotation of Earth make two electrostatically charged bodies interact magnetically (with each other)?
Does the rotation of Earth make two electrostaticaly charged bodies fixed on its surface interact magnetically (with each other)? If yes, is this interaction different as geographical latitude changes?...
- 1,815
2
votes
0
answers
55
views
Should the velocity increase or decrease?
Suppose some projectile is traveling along the positive $x$ direction at a velocity $v$. While moving it is emitting particles, and thus losing mass. If the particles are being emitted in the same ...
- 1,791
0
votes
0
answers
76
views
Doubt regarding derivation of rocket equation
I'm having quite some issues deriving the ideal rocket equation, and I suspect it is due to lack of identifying scalar terms and vector terms. Here is how I derive it :
Let $v$ be the velocity of the ...
- 1,791
0
votes
1
answer
98
views
Can a bubble of vacuum move through space?
If there are really regions in space where a vacuum exists, I have learned there can still exist electric and magnetic fields within. That makes this region then differentiable from the regions around ...
- 103
16
votes
10
answers
5k
views
Why do bodies traveling at constant velocity experience the same physics?
I am new to special relativity. I don't have a background in physics.
I was reading Brian Green's The Elegant Universe and got hung up on an example.
In fact, Einstein realized that the principle of ...
- 279
0
votes
1
answer
111
views
Distance between two airplanes [closed]
I need help with a vector problem where my solution is different from that of my teacher. The translation of the problem reads as follows:
An air traffic controller observes two aircraft on his radar ...
6
votes
3
answers
516
views
Interesting answer as a range of tension in pulley-block-plane system
I want some intuitive understanding on why there will be a range in tension in the below question. (On solving we will get that the system is at rest ($a=0$) and since its starts from rest the blocks ...
- 95
0
votes
1
answer
557
views
Calculating the velocity of a tennis ball after impacting a moving racket
Suppose I have a tennis ball moving with $v_1$ (blue arrow in first image below) impacting a moving tennis racket with velocity $v_r$ (black arrow in first image below)
In order to calculate the ...
- 103
1
vote
2
answers
46
views
Power Demand for Motion of Vehicle on a Road and Plain in Air with Air Resistance
Let's say we have an ideal motorcycle without frictional losses (no tire slip, ideal machine without losses). But we want to consider wind force which is proportional to the square of speed
$F = k \...
- 1,299
4
votes
3
answers
551
views
Charges and relative motion
We know that coulomb charge can't be applied on charges in motion. Why? What if they are moving in same velocity? Aren't they actually at rest for each other? ( yeah, it depends upon medium, so I'm ...
0
votes
5
answers
493
views
Is rotational motion relative, as is linear motion?
In special relativity only relative velocity is what matters. A rocket and the universe can be in relative linear motion. In the rocket the universe is in motion. The universe got this motion when it ...
user307025
0
votes
1
answer
434
views
What is the velocity of a photon with respect to another one? [duplicate]
When light comes from a source, there are numerous photons associated with the energy packets.
Now, what is the velocity of a single photon with respect to another photon coming form the same source i....
-2
votes
2
answers
445
views
What would an outside observer see if I throw a ball in the opposite direction of the train's movement towards a catcher? [duplicate]
Without taking air resistance into consideration, what would a stationary observer see if I am inside a moving train traveling at 60mph and throw a ball at 60mph opposite the direction of the train? ...
4
votes
1
answer
151
views
Relative Circular Motion [duplicate]
Four particles $P_1, P_2,P_3,P_4$ are moving in a plane. At $t=0$, they are at the four corners of a square $ABCD$ of edge length $l$. Each of the particles has a constant speed $v$. The velocity of $...
- 345
1
vote
0
answers
114
views
Work done on a moving cart in wind
Let us suppose a cart is moving in a rough ground with a propeller attached to the roof of the cart.
Let the velocity of the cart at the given point of analysis be V and velocity of wind is -W. The ...
0
votes
1
answer
107
views
CoM-and-relative velocity
In our scrip we are considering the elastic collision between two particles, one with inital velocity $\vec v$ and the other $\vec w$. We also consider that the particles have the same mass.
...
- 1,398
3
votes
2
answers
279
views
Can we use relative motion if acceleration of two bodies are different?
Suppose, on the $x$-axis, a body $A$ is moving with velocity $v_1$ and acceleration $a_1$, and a second body $B$ is moving with velocity $v_2$ and acceleration $a_2$. $B$ is at a distance of $S$ from $...
3
votes
2
answers
67
views
Relative Velocity (Kinematics) [closed]
I was studying the concept of relative velocity and after solving a few problems I am running into this confusion.
a) Let’s say two cars are moving perpendicular to each other (no collision) with ...
- 31
-4
votes
2
answers
89
views
(Misunderstood) special relativity and equivalence of motion [duplicate]
Let $A$ be the person who is standing on the Earth (ignoring gravitational field, etc.). Let $B$ be the person who is moving to the Proxima Centaura and back. By the time dilation equation we get:
$$...
- 1,188
7
votes
1
answer
418
views
How to calculate relative velocity in curved spacetime?
Is there a nice geometric way to calculate relative velocity in curved space time? I'm looking from something similar to how the separation vector $n$ between $2$ neighboring geodesics obey:
$$ \...
- 1,389
2
votes
3
answers
675
views
I am moving right and rain is falling vertically down.Why should I hold umbrella at an angle?
This is related to relative velocity.I get that, from my moving frame of reference rain is making an angle.But still... it doesn't make sense to hold umbrella at an angle when rain is falling ...
0
votes
0
answers
117
views
If motion is relative, can we say that the Earth doesn't revolve around the Sun? [duplicate]
Considering motion to be relative, consider these two cases as follows
An observer is standing on the sun and observing the earth and the earth has no background (no stars and stuff in the background)...
- 183
5
votes
5
answers
1k
views
How should I understand the idea of relativity of space?
In the book General Physics by L.D.Landau, he mentioned the following in the first and second paragraph
The fundamental concept of mechanics is that of motion of a body with
respect to other bodies. ...
- 138
0
votes
0
answers
24
views
Sliding Friction Force
Sliding friction force is not dependent on velocity. Is wear dependent on velocity? For example, it takes 10 Newtons to overcome sliding friction, no matter if the relative velocity is 1m/s or 1000m/s....
-1
votes
1
answer
71
views
Velocity of a swimmer relative to the Earth [closed]
Julia can swim 0.34 m/s in still water. She swims directly east across a river that is 180 m wide and lands at a point that is 81 m north downstream. Determine Julia's velocity while swimming relative ...
1
vote
1
answer
124
views
Velocity of an object with respect to the same object
I know that velocity of an object with respect to the same object is a null vector but I'm not able to get a grasp of it.
Whatever I had thought till now is that if I'm sitting in a train (which may ...
- 882
0
votes
3
answers
118
views
Relative Motion and Motion on ground
When I walk on the ground I know that it's me who is walking and not that I am just moving my legs forward and backward and the ground is moving.But according to relative motion I should not be able ...
- 103
1
vote
2
answers
7k
views
What will be the minimum drift possible when a boat crosses a river? [closed]
Imagine a boat with a constant speed $v$ that has to cross a river of width $d$. Let the river flow with a constant velocity $u$. I want to know the angle at which the boat should sail in order to ...
-1
votes
1
answer
101
views
Measuring the speed of an object
If I understand correctly someone said (Einstein?) that all motion is relative. However, if it were possible; given that light always travels in a vacuum at a fixed speed, could all other motion be ...
- 719
2
votes
1
answer
66
views
How would we know whether a object is moving in deep space?
In deep space, there isn't anything we can compare our position with (According to my knowledge). In other words, we won't be able to define an origin so how would we know whether we are in motion or ...
- 883
1
vote
4
answers
83
views
How can we tell if a charge is moving in a Magnetic Field?
In the equation $\vec F=q\vec v×\vec B$ ($\vec B$ is the magnetic field), what is $\vec v$ with respect to?
If we were to imagine $\vec B$ to be infinitely large. How could we tell if the charge is ...
- 11
0
votes
2
answers
91
views
Why does these two masses not have same acceleration? [closed]
Assumptions: No friction , $m_2$=5kg and $z_1$=2kg. $z_2$ is fixed at its place.
Here, there is a mass of $5kg$ on a movable wedge of mass $2kg$. So, my question is that can we say that acceleration ...
- 33
1
vote
1
answer
169
views
Acceleration and geodesics in General Relativity
Consider this situation:
A) An aeroplane travels a distance from point A to point B which are located on the opposite sides of the Earth. The aeroplane has taken the shortest possible distance to ...
- 159
4
votes
1
answer
1k
views
Is work done by the internal forces independent of the frame of reference?
This question is about work done being dependent on the frame of reference, which is, obviously the net work done.
I ask what is the reason for the work done by internal forces to be independent of ...
- 362
0
votes
1
answer
35
views
Using rate and per unit time together for describing effects of motion
I have observed recently 3 different elementary definitions of velocity
Rate of change of position, change in position per unit time ,and
rate of change in position with respect to time,so I am not ...
1
vote
1
answer
105
views
A question on time taken in different frames of references
Let us say , a swimmer has to swim upstream and downstream a river , between two points which are at distance "L" from each other . The swimmer can swim in still-water at velocity "Vs&...
- 123
1
vote
2
answers
428
views
Apparent wavelength received by observer in doppler's effect
I have a few doubts about Doppler's effect.
Does the apparent wavelength received by the observer depend upon whether the observer is moving or not?
$λ_{apparent}=\ \frac{v_{sound}\pm v_{source}}{f}$....
- 292
0
votes
0
answers
3k
views
On a rainy day, a man is running on a hilly terrain in such a way that he is always finding the rain drops hitting him vertically
It is assumed that rainfall is uniform in the whole terrain from O to E(figure attached) When the man was at rest on stretch OA, he found the rainfall at an angle of $30^o $ with the vertical.
What ...
- 309
1
vote
2
answers
184
views
Very basic special relativity (relative velocities)
My question involves broadly why calculating different (Einstein) relative velocities give different answers:
Say we have car 1 traveling in front of car 2. Car 1 goes at velocity $3c/4$, while car 2 ...
- 111
0
votes
1
answer
278
views
Relative position from two reference frames
Here, clearly $\vec{r}_{S'S} + \vec{r}_{PS'}= \vec{r}_{PS}$. Then we differentiate and double differentiate and get the standard equations of relative velocity and acceleration.
Now according to my ...
- 45
1
vote
1
answer
40
views
Why do we say the resultant vector as the relative motion in this case?
If a car A moves with acceleration $2m/s^2 $due east and car B moves $1m/s^2 $due north. What would be the acceleration of car B with respect to car A. Now , for this. The solution in my textbook is ...
- 294
0
votes
1
answer
41
views
Velocity Gradient and Force in Air
I have experienced that when we go on a bike at a high speed, keeping our hands close to the surface of the bike is not much a problem and we feel negligible force which the air applies on us. But as ...
- 11
-1
votes
2
answers
83
views
Do time dilation affects motion? [closed]
I know it doesn't but why not? Imagine when time dilation becomes Infinite then everything will stop or not? What will happen to a ball which hypothetically move at the speed of light so that space ...
- 483
0
votes
3
answers
1k
views
Does Coriolis effect change the direction of an object moving parallel to equator, say along the tropic of Cancer?
It is usually said that the Coriolis force deflects a horizontally moving object to its right in the northern hemisphere and to the left in the southern hemisphere, and an object at the equator will ...
- 337
0
votes
4
answers
3k
views
What is Relative and Absolute? [closed]
I was studying about relative motion, and randomly thought about What actually is a Relative Term or a Absolute Term. So far in the school book it is written that, Quantities that depends on a ...
- 31
0
votes
0
answers
45
views
Speed of one frame with respect to another in special relativity [duplicate]
To derive the Lorentz transformation we begin with the general relationship between two frames as below:
$x' = Ax + Bt$
$y' = y$
$z' = z$
$t' = Cx + Dt$
If frame $S'$ is moving at speed $v$ with ...
- 1,270
0
votes
1
answer
39
views
${}$Reference frames [duplicate]
Most of the particles have different velocity in different reference of frames but why is speed of light the same in all refrence frames? After all light is made of a photon.
2
votes
2
answers
131
views
Can I apply Newton's equations of motion to relative motion?
We know that
Velocity of A relative to B is
$$ \vec v_{A|B} = \vec v_A - \vec v_B $$
and Acceleration of A relative to B is
$$ \vec a_{A|B} = \vec a_A - \vec a_B $$
So, is it correct to do this to ...
- 227
0
votes
3
answers
133
views
Question regarding relative velocity of muzzle bullet? [closed]
A police jeep is chasing with, velocity of 45 km/h a thief in another jeep moving with velocity 153 km/h. Police fires a bullet with muzzle velocity of 180 m/s. The velocity it will strike the car of ...
- 725
0
votes
1
answer
33
views
Determination of the speed and angular velocity of 4 rolling cylinders between planks
According to the picture, there are four identical cylinders, with radius R, that are rolling without slipping at every contact point. The upper plank is moving with speed 2v (m/s) towards the right, ...
- 1