All Questions
Tagged with relative-motion vectors
47
questions
1
vote
2
answers
59
views
Euler Rotation Equations and invariance of vectors in different reference frames
Consider two frames, one which is inertial and the other one rotating w.r.t. to the inertial frame. Say there is a rigid body having angular momentum which is same/invariant in both frames. How is it ...
- 11
0
votes
1
answer
44
views
The locus of the velocity vectors of a boat navigating in the sea under the presence of a very strong wind?
I already asked a question very similar to this one here and I think the solution would not work when the boat navigates in the sea when a very strong wind blows. That is I am trying to find the ...
- 159
1
vote
1
answer
60
views
Simple classical mechanics problem to compute minimum distance attained between two ships moving with constant velocity
I have been reading the book "A Course in Classical Physics 1 - Mechanics" by Alessandro Bettini. I have reached a problem in the first chapter that I am having trouble with.
The problem ...
- 121
3
votes
3
answers
515
views
Relative velocity related to acceleration
Let's say we have a car moving on the horizontal ground with a velocity of $10 \hat{i} \frac{m}{s}$. A person inside throws a ball vertically upward with a velocity of $3 \hat{j} \frac{m}{s}$. Now I ...
- 169
0
votes
3
answers
239
views
A question about relative motion and how to make sense of it
So, here is the question:
Assuming the 2D Cartesian system and the basis vectors $\hat{i}$ and $\hat{j}$, we have two cars A and B located at (0,6) and (-30,0) respectively. Car A starts moving with a ...
- 169
0
votes
1
answer
95
views
For an airplane moving north from some latitude (say $30^{\circ}N$), why does rotation of the Earth cause an increase in apparent drag?
I'm not able to understand the answer to this example:
Example 10 from the Curtis Orbital Mechanics text book :
An airplane of mass $70 000\ \mathrm{ kg}$ is traveling due north at latitude $30^\circ$...
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 ...
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 ...
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
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 ...
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
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
-1
votes
1
answer
52
views
Why is direction of train like this for car?
This is an image of a train and a car. T is the train moving towards - $x$ axis and C is the car moving towards $+ y$axis.
So, my teacher made a resultant velocity with $-5\hat i$ and $-20\hat j$. ...
- 725
-1
votes
2
answers
40
views
Is this correct regarding velocity of train?
So many yellow T drawn are just different position of train at different instants.The person is standing still at all those instants at one place.
If a train is moving at 5m/s.
Then for me , can we ...
- 725
0
votes
1
answer
38
views
Direction of $V_RM$ confusion
So ,please read both the questions . They have similar originate questions that I am facing difficult in.
Let us say rain is falling downwards with v = -5j and a man is moving with a velocity of 2i in ...
- 725
-1
votes
2
answers
91
views
Not able to understand relative velocity in 2dimension?
I have a body A = 4j and B = -3i
Their relative velocity = -3i-4j.
But the position is somewhere they both don’t even meet.
It should be from B to A but it form C to A or B.Not able to understand what ...
user280997
-2
votes
1
answer
69
views
Problem regarding relative velocity [closed]
Train A moves north with speed 54km/h. What is the velocity of a monkey running on roof of a train A against its motion (with velocity of 18km/h with respect to A)as observed by a man standing on ...
- 47
1
vote
0
answers
80
views
Vector addition of drone affected by wind
I've been struggling with this calculation for around a week and am starting to question whether or not it's even possible.
What I want to do is find the bearing and speed a drone will need to fly at ...
- 11
0
votes
3
answers
103
views
A textbook problem on vectors [closed]
I am stuck on a textbook problem on vectors (a new topic for me). The problem given in my book says:
A man can swim with a speed of 4 km/h in still water. How long does he take to cross a river 1 ...
user236322
-6
votes
1
answer
113
views
An Evil Vector Problem! [closed]
A person is walking on straight road starting with a velocity $v$, the direction of of air ,observed by him makes an angle $\alpha$ with his is direction of motion. Now during the race, he finds ...
- 115
1
vote
1
answer
887
views
Time when two particles will meet [closed]
Particle P moves with constant speed of 13m/s always aiming at O . As P starts moving , O moves with constant velocity of 5m/s towards positive y-axis. Time taken by particle P to catch O will be?
I ...
- 29
1
vote
1
answer
100
views
Signs in relative vector addition
So I know the formula for relative vector addition is
$$w = \frac{v-u}{1-\frac{uv}{c^2}}.$$
How do I chose when to use this formula or its inverse transformation for solving vector addition problems ...
- 33
-1
votes
2
answers
4k
views
What does speed of an object relative to water mean?
A swimmer swims with the velocity 1.25 m/s "relative to water". He has to swim across the river which is 150 meters wide. If his direction of velocity is perpendicular to the stream, he is taken away ...
- 203
0
votes
1
answer
605
views
Is this Question correct? Newtonian Motion - Relative Motion of Rain
There is a question in a textbook which states:
"A cyclist is riding north at 12km/h when it starts to rain. The rain appears to be falling towards her at an angle of 10 degrees relative to the ...
- 57
1
vote
3
answers
6k
views
Relative motion involving angle
Suppose I am going in a direction with a velocity $v_1$ and my friend is going in a direction which makes an angle of $A$ with my direction with a velocity of $v_2$.
Then what will be my relative ...
- 1,400
0
votes
3
answers
76
views
Reference Frames
I observe two cars approaching each other from opposite directions and measure as 40 mph and 30 mph, respectively. How fast is the 40 mph car moving according to the driver in the 30 mph car? ...
- 19
1
vote
1
answer
2k
views
What is the speed of a swimmer in a river when he wants to travel the minimum distance?
The speed of the swimmer in still water is $v$ and that of the river is $u$ ($v>u$). He should travel at an angle $x$ with respect to the direction perpendicular to the river's flow, towards the ...
-1
votes
1
answer
168
views
Apparent velocity of winds
If I run north at 10j m/s and the wind is also blowing north at 2j m/s, then do I feel a wind of 8m/s in my face if the relative velocity of the wind to me is -8j m/s ?
- 103
0
votes
3
answers
477
views
Kinematics: relative velocity [closed]
The question goes like this:
An aircraft, with velocity 580 km/h, is supposed to follow a straight path in the direction 38,0° in the northeast (measured from the east). The aircraft experiences a ...
- 118
0
votes
2
answers
126
views
If a boat can travel at 10 mph in a river with no current, will it always be moving 10 mph compared to the water at full speed, regardless of current?
I must be confused, because it seems to me that the boat would always be traveling 10 mph in relation to the water regardless of the water's velocity, but the answer key for my assignment states the ...
- 127
1
vote
1
answer
611
views
How does one solve a 2D relative velocity problem given 3 angles and 1 magnitude?
Most of it is the title. To be a bit more clear, I am asking about a problem involving two traveling objects. The question gives you the angle of motion of both objects relative to the earth, and the ...
- 175
3
votes
1
answer
4k
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:
$$\mathbf{r_A}=\begin{pmatrix}r_{A_{x}}\\r_{A_{y}}\\r_{A_{z}}\end{pmatrix}$$
$$...
- 133
0
votes
1
answer
288
views
Why the point right below the center of a rolling ball on the ball has zero instantaneous velocity [duplicate]
Suppose there is a snooker ball rolling on a table. The velocity of the center of the ball is Rω and its direction is horizontally right. I don't understand why the point right below the center on the ...
- 23
1
vote
1
answer
3k
views
Problem on relative motion involving wind speed .Finding the real velocity of wind?
Here is the question
For a person running west at 7km/hr wind appears to blow from north-west .But when he walks towards west at 3km/hr the wind appears to blow from the north. What is the true ...
- 31
0
votes
1
answer
1k
views
Relative Motion of Child and Boat [closed]
A boat is traveling upstream at $11~\text{km/h}$ with respect to the water of a river. The water is flowing at $7.0~\text{km/h}$ with respect to the ground. What are the
(a) magnitude
(b) ...
- 249
1
vote
1
answer
113
views
Speed with wind resistance
This is probably a basic question, but it has been a while since I did anything like this.
If a boat is sailing forward at speed $x$ and the direction of the wind, with magnitude $y$, is either equal, ...
- 11
1
vote
1
answer
3k
views
Finding resultant and direction of resultant
In this question-
A motorboat is racing towards the north at 25km/h and the water current in that region is 10km/hr in the direction of 60 degrees east of the south. Find the resultant velocity of ...
- 715
3
votes
3
answers
878
views
What is the relative velocity of this plane relative to the helicopter? [closed]
There is a plane moving 100 m/s due east relative to the ground without vertical motion. There is a helicopter facing north moving straight up at 20 m/s. From the perspective of the helicopter, is the ...
user57358
1
vote
1
answer
4k
views
Kinematics simple question [closed]
Question: In order to protect himself from the rain, a person is standing holding an umbrella at right angle to the horizontal surface. The rain is falling at 10m/s when the velocity of the wind is ...
- 1,582
4
votes
1
answer
32k
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 ...
- 155
0
votes
2
answers
1k
views
Relative motion. Setting course of closest approach
Let $r_{P/Q}$ be the position vector of $\overrightarrow P$ relative to vector $\overrightarrow Q$ and $v_{P/Q}$ the velocity vector of $\overrightarrow P$ relative to $\overrightarrow Q$.
Suppose $|...
- 238
0
votes
1
answer
24k
views
Relative motion and how to calculate magnitude and velocity of objects relative to different given objects [closed]
A canoe has a velocity of 0.550m/s southeast relative to the earth. The canoe is on a river that is flowing at 0.540m/s east relative to the earth.
Alright so I attempted many different things an ...
- 49
0
votes
1
answer
2k
views
Finding an equation to solve for the velocity of a swimmer crossing a river [closed]
Where $\theta=45^\circ$, $d_1=200\:\mathrm{m}$, and $d_2=150\:\mathrm{m}$.
I do not know how to combine the following equations:
$$\begin{align}
t&=\frac{d_1}{v_s\cos(45^\circ)}\\
t&=\frac{d_2}...
- 49
0
votes
2
answers
679
views
Relative velocity of boat
I am trying to understand fully the following question:
A boat is traveling west at 100m/s and is partially helped by a strong wind blowing at 20m/s 30 degrees north of west. What speed could the ...
- 316
3
votes
2
answers
4k
views
I don't understand the idea of perpendicular vectors being independent of each other?
So problem 71-75 is about vectors. The problem says:
A river has a current flowing with a velocity of 2.0 meters per second due east. A boat is 75 meters from the north riverbank. It travels at 3.0 ...
- 189
2
votes
1
answer
6k
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 should ...
- 1,128
-3
votes
1
answer
13k
views
man walking in rain:relative velocity [closed]
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 ...
- 1,128