Questions tagged [relative-motion]

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special relativity - relative motion of two objects [closed]

I'm stuck in this exercise. I don't know how to proceed. Any hints I appreciate it. Two bars of the same proper length $L$ moves in the same way on the $x$-axis. In the reference frame of one of the ...
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1answer
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Swing in moving truck

I was just thinking about a situation in which a big truck is moving in high speed say ( $80 \ miles/hr$). There is a swing attached with the ceiling of the truck container which can move freely in ...
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Pursuit curve on a sphere [closed]

One day I thought about chasing curve on a sphere. I wanted to find parametric equations such as $\theta (t)$ and $\phi (t)$ of running dog always towards a rushing cat on a big spherical world. ...
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What's the name of the hypothesis that states that instead of the universe expanding, all matter is shrinking? [closed]

I recall a few years ago there was such a hypothesis I read about. No longer do I remember the name though. Can anyone help me out?
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Calculating unknown Relative Velocity from Given 2 Known Relative Velocities for speeds comparable to speed of Light

Dear fellow physics lovers, Given 3 objects A, B and C, travelling with relative velocities such that $\vec{v_{AB}}$ = Velocity of Object A with respect to Object B $\vec{v_{BC}}$ = Velocity of Object ...
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1answer
39 views

Kinematics in moving reference frames

Assume we have an object moving along a path $p_W(t)$ that is described in some fixed reference frame $W$. If we now have a second reference frame $B$ which differs from $W$ by some time varying ...
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3answers
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Why the relative motion goes wrong here?

This is a question from jee advanced. I followed the approach of relative velocity In the frame of rocket we can write $s_{rel}$=$u_{rel}t$ since acceleration of both the particles is 0 in this frame ...
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3answers
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Doesn't this experiment signify that inertial frames are not equivalent? [duplicate]

While reading about kinetic energy something poked in my mind. When we talk about kinetic energy of a body, it is actually the combined kinetic energies of all the atoms in that body. Now suppose a ...
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Relative Motion in Two Dimensions

There's a problem that I've been working on in physics for a couple of days now, and I'm just wondering if my thinking is wrong here. Say you're given the velocity of an object (with an x- and y-...
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1answer
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Relativistic or non relativiistic mechanics?

Question: A train of length $l=350 metres$ starts moving rectilinearly with the constant acceleration $a=3×10^-² ms^-²$; $t=30s$ after the start the locomotive headlight is switched on $(event 1)$, ...
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Motion of Points around a Triangle [closed]

I came across this problem in the book "Problems in General Physics by IE Irodov"- Three points are located at the vertices of an equilateral triangle whose side equals s. They all start ...
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Velocity Question from grandparent

My Grandparent asked me this question a few years ago, and I am getting around to giving him an answer, but I don't know the answer. Can anyone help? "A pickup truck is speeding along a highway ...
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Relative motions, between inertial and non-inertial frames or bodies

I had no other way to put my problem to you guys thus I am taking an example.... Here, ...
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3answers
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Coriolis effect vs preservation of angular momentum on merry-go-round, sniper's bullet, hovering helicopter and high altitude rockets

I understand that how helicopter hovers at the same position or a thrown ball falls to the same position even though earth is spinning. This is due to the preservation of angular momentum and my ...
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4answers
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Why motion is not absolute or relative to space?

We say that motion isn't absolute.but why?if we measure motion relative to "space" it will be absolute for all observers. isn't it? Is space also relative like motion? If space has no "...
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3answers
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Is the frame of elevator Preferred over the frame of ground? [closed]

When an object is thrown upward with some velocity then it doesn't fall towards the earth until the given velocity becomes zero. Now imagine the case given in the figure There is a question in my ...
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2answers
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How to decide which velocity is bigger in a collision before writing velocity of approach and velocity of separation?

My teacher said that velocity of separation is $V_1$- $V_2$ where $V_1$ is greater than $V_2$ and said same for velocity of approach. The problem is how would you determine which velocity is greater ...
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1answer
65 views

Relative angular velocity of one point with respect to another on a solid rigid body [closed]

What is relative angular velocity of A wrt B and that of A wrt C in the figure given below? Description: A, B and C lie on a solid cylinder(rigid body) rotating with a constant angular velocity $\vec{...
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Flying a drone in a moving car/airplane

Why does a drone fly with respect to the air in a moving car/airplane, but not in an elevator as shown in this clip: What Happens If You Fly a Drone In An Elevator? I understand that the drone will ...
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1answer
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Magnitude of relative velocity between two frames in special relativity

It seems to be taken trivially, and it is indeed intuitive, that the relative velocity $v$ of some frame $O$ with respect to $O'$ is the same in magnitude to the relative velocity of $O'$ with respect ...
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2answers
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Relative speed of galaxies in deep space

Let say we observe two galaxies, one little bit closer to us than the other one. If we calculate the speed of the farther one does it mean that according to the Hubble law when the closer one reaches ...
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4answers
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Does Relativity make a difference on whether Earth revolves around the Sun or not?

According to the theory of relativity there is no ultimate preferred frame of reference in our universe. It means that whenever there is motion between object A and object B, whether it is considered ...
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How can different points on a rigid body move with different speeds but also be relatively at rest?

For a rigid body rotating with a constant angular speed, the points near the axis must have lower linear velocity than the points farther away. If they have different linear velocities, they must have ...
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1answer
114 views

Why is the following equation not correct? [closed]

Q)Point A moves uniformly with velocity $v$ so that the vector $v$ is continually "aimed" at point B which in its turn moves rectilinearly and uniformly with velocity $u<v$. At the ...
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Relative Velocity of two particles [closed]

If two particle are neither approaching towards nor receding away from other then their relative velocity is non zero. How is this possible??
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2answers
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Change in Kinetic Energy in two different reference frames (one of them non-inertial) [duplicate]

Let's say an object of mass 10 kg is fired from a cart of mass 90 kg. The object and the cart, of total mass 100 kg were initially moving together with a speed of 10 m/s. Then, the object is fired by ...
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1answer
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Magnetic field and frame of reference [closed]

A charged particle moves with a velocity near a wire carrying an electric current,and suppose I see the particle from a frame moving with same velocity in the same direction . I will see the charge at ...
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2answers
35 views

Does a magnetic field (moving relative to the charge) act on a stationary charge? [duplicate]

Does a magnetic field moving relative to a stationary charge act on it?
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2answers
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Why distance between 2 particles is independent of frame?

I was solving question in kinematics related to minimum distance between particles there they said that distance between two particles is independent of frame the distance they both measure between ...
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Spinning observer inside a solenoid paradox?

It is well known that magnetic fields are frame dependent, with an observer travelling parallel to a moving point charge experiencing no field. Similarly for a solenoid, a stationary observer on the ...
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2answers
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Do the time taken to travel a fixed distance changes in two different inertial frame of reference in relative motion

I have calculated time taken to travel a fixed distance by the object from two different frames of refrence. One frame was moving with uniform velocity wrt other . But time taken to cover the equal ...
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1answer
54 views

Why is heat energy dissipation in two intervals frame dependent?

The question asks for heat produced in the given specific conditions. It seems like an application of the work-energy theorem with friction doing work on the block and dissipating the heat in the ...
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2answers
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Why don't hovercrafts move West relative to the Earth [duplicate]

Suppose that there is a hovercraft floating a few centimetres above the Earth's surface. As it is disconnected from the Earth, which is spinning from West to East, shouldn't it appear to move East to ...
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2answers
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Upstream and downstream problem using relative velocity

On a river coast, there is a port; when a barge passed the port, a motor boat departed from the port to a village at the distance $S_1 = 15$ km downstream. It reached its destination after $t = 45$ ...
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2answers
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Who applies the force on the things moving backward that we see when moving forward? [duplicate]

When we move forward in a car, things around us move backward. I understand some force is being applied on the car that is the reason for its forward movement. But what is the source of force on the ...
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2answers
31 views

Force equations for a particle in a non-inertial frame of reference

I am familiar with Pseudo forces and how we use them in accelerating reference frames. My question is a bit specific. Let’s say I am accelerating at $a\frac{m}{s^2}$ and holding a tennis ball of mass $...
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1answer
63 views

Forces acting on a book on a moving table [closed]

I’m studying for an upcoming physics exam and one of the sample questions essentially boils down to this: a book (not clamped on) is on a table that is moving to the left. Is there a force of static ...
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1answer
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Reasoning pseudo force due to accelerating car mathematically [closed]

For a person inside an acceleration car, his acceleration inside the frame is $a_{\text{rev}}$ , outside the car is accelerating at $a_{\text{car}}$ and person inside is accelerating at a rate of $a_{\...
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5answers
263 views

Time dilation in a moving frame of reference

According to the theory of relativity, time slows down in a moving frame of reference. But I am confused in the example given below. Suppose there are two men $A$ and $B$. $A$ is standing in moving ...
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2answers
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Why do two objects at distance of closest approach have equal velocity?

So, Here is a proof I came up for it, Define relative position function $x_1$ is position of body-1 and $x_2$ of body-2: $$x(t) = x_2 (t) - x_1 (t)$$ Then finding the maxima of this function leads us ...
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4answers
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Co-efficient of restitution

Co-efficient of restitution is defined as $\displaystyle\frac {Relative \ velocity \ after\ collision}{Relative \ velocity\ before\ collision}$ so lets consider two bodies A and B moving with ...
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2answers
53 views

What does an observer in a reference frame moving with velocity of light see, when another reference frame with velocity c is launched in opposite? [closed]

Suppose a reference frame is moving with velocity c in +x direction. An observer is there. At any time instance, another reference frame with velocity c is launched in opposite direction, i.e. -x ...
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2answers
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Which should be the correct option? [closed]

Question-- A person standing on the floor of an elevator drops a coin. The coin reaches the floor of the elevator in time t1 if the elevator is stationary and in time t2 if it is moving uniformly. ...
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Taylor's Classical Mechanics - Confusion About Reference Frame

I am hoping to dig a little deeper into what Taylor says on page 9 of Classical Mechanics. I've provided an excerpt just below: A more important difference arises when two frames are in relative ...
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1answer
29 views

Relative velocity during a collision

I quote Resonance Kota module on Mechanics(Vol.1): The collision is just avoided if relative velocity becomes zero just at the moment the two cars meet each other. I don't understand why should it ...
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1answer
37 views

Observing from a jumping frame of reference

Today, I was doing some exercise and started with jumping (normal jumping). The exact situation was something like this: I was standing in front of a window, at my eye level, behind it was my ...
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1answer
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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 ...
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1answer
33 views

Relative velocity of a particle under uniform circular motion

The question is based on fairly simple mechanics principles but seems to have no definite answer. Suppose there is a point particle A at a point X and around it another particle B in uniform circular ...
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2answers
139 views

If you could fly, at what point would you see the Earth rotate?

If we could fly away from the Earth (imagine Superman), at what point would we notice the Earth's spin (or at what point would be stop moving along with the Earth)? Or is that just not how relativity ...
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11answers
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How can any speed be defined as a constant? [duplicate]

We know that the speed of light is a constant, and can therefore be used to calculate many other relative values, but I'm having difficulty understanding how speed can be a constant, seeing as it's ...

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