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3 answers
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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??
UM Desai's user avatar
  • 318
5 votes
4 answers
229 views

Is this a kinematics paradox?

You consider a shaft which can rotate freely (there will be of course a frame with ball bearing to hold the shaft firm and to allow it to rotate with low friction); fixed on this shaft there are two ...
Landau's user avatar
  • 768
2 votes
1 answer
362 views

What is the reactionary force exerted on a swing?

On a playground swing, children quickly learn how to swing higher and higher by timing their body motions with the resonant frequency of the swingset. But it occurs to me that it seems you're making ...
TheEnvironmentalist's user avatar
3 votes
3 answers
893 views

Newton's Second Law in vertical launch of a rocket

Consider a rocket being launched vertically. Let $T(t)$ denote the thrust from the engine and $M(t)$ be the total mass of the rocket at time $t$. At $t=0$, $T(0)=M(0)g$ (so that the normal force due ...
Chern-Simons's user avatar
  • 1,047
0 votes
2 answers
466 views

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 ...
prateek maurya's user avatar
4 votes
1 answer
780 views

Is Centripetal Velocity a Thing?

I'm quite new to physics so this question may sound dumb for many of you. But when I was learning about uniform circular motion, all sources I can find talks about centripetal acceleration, and, when ...
Nicholas's user avatar
  • 143
3 votes
1 answer
137 views

Average Velocity ($\vec{\bar{v}}$) Intuition and Analogy for Non-Uniform Acceleration

Background So I was trying to make as much sense out of kinematics through intuition after having taken my first semester of university physics, and I've stumbled onto a dillema that I can't seem to ...
Naganite's user avatar
0 votes
1 answer
83 views

why the velocity in some constrained motion is greater than the provided velocities? [closed]

Suppose the string provided is inextensible and massless. The velocity of $C$ is $2$ m/s and the angle theta is $37^\circ$ then we get the velocity of ring $A$ to be $v = 2/ \cos37^\circ$ i.e. $10/4$. ...
Prakhar Agrawal's user avatar
1 vote
1 answer
153 views

Finding The Trajectory of particle Kept on a rotating surface

Suppose we "Keep" a particle on a circular, rotating turn-table, rotating with constant angular velocity $\dot{\theta}$, (i.e, the at $t=0$,when the particle makes contact with the table, the ...
satan 29's user avatar
  • 1,325
2 votes
1 answer
128 views

Does mass matter at all for kinematics vertical questions w/o friction?

This is the specific question w/o information on mass given, I think here is not enough info. A block and a sphere are each released from rest at the top of an incline from the same height. The ...
Alexander Ye's user avatar
2 votes
3 answers
246 views

Why does this example seem to contradict conservation of energy?

Consider a 10 kg box on the bed of a truck accelerating at 1 m/s^2. Consider a reference frame where it starts at 0 m/s and ends at 10 m/s and then consider a reference frame where it starts at -5 m/s ...
Hrishabh Nayal's user avatar
-1 votes
1 answer
40 views

Vertical motion [closed]

Ball $A$ is thrown vertically upward from the top of a $30$ m high building with an initial velocity of $5$ m/s. At the same instant, another ball $B$ is thrown upward from the ground with an initial ...
Ian Attygalle's user avatar
1 vote
3 answers
44 views

Considering body as a paricles, how the force is applied?

Lets consider a 2d box with nothing inside of it - just 4 walls, which consist of balls, connected by the force very similar to spring force. Look at the picture I draw. When the force applied to ...
Artur's user avatar
  • 143
2 votes
1 answer
114 views

Calculate local linear accelerations from trajectory

I'm trying to simulate linear accelerations and angular velocity of a vehicle which drives on a flat surface. For this, I want to use a trajectory consisting of position ($x_i, y_i$) and orientation $\...
RobinW's user avatar
  • 123
0 votes
1 answer
319 views

Path of an object in gravitational field [duplicate]

How do you prove that path of a satellite or a planet is a second degree curve? In other words, how do you prove Kepler's law which states that planets move in elliptical paths?
Srikar Anand Yellapragada's user avatar
3 votes
3 answers
444 views

Velocity after applying a force in the vacuum

I’m sorry for so simple question, but I just need to be sure. I understand, that the changing of the speed occurs only when the force is applied, I understand that if one punch a ball in the free ...
Artur's user avatar
  • 143
1 vote
1 answer
76 views

Determining acceleration in order to meet a space-time-velocity reservation

An Example A train on a single line track is told to be at position $x_{res}$, at time $t_{res}$, and to be moving at exactly $v_{res}$ when it hits that point. Where $_{res}$ denotes the reservation....
Torantula's user avatar
0 votes
1 answer
148 views

Rigid bodies: angular velocities, momentum, Inertia Tensor, rotational kinetic energy. Books suggestions? [duplicate]

I'm having a hard time with understanding how to model the rotational kinetic energy of rigid bodies. I will appreciate any good suggestion about resources such as books or videos regarding topics ...
0 votes
3 answers
678 views

Kinetic Energy and Braking Distance [duplicate]

A car traveling at 50km/h will move 44 extra meters from the moment its brakes are applied fully. If the same car travels 100 km/h on the same road, how far will it move from the instant its brakes ...
YEET's user avatar
  • 21
0 votes
0 answers
91 views

How can I isolate the drag constant (C) for vertical motion with quadratic drag from the equation for peak height?

Some background on my problem: I have calculated the peak height of a rocket (with quadratic drag). As this will be used for a PID software application, I need to have the equation be expressing peak ...
Joshua's user avatar
  • 101
1 vote
1 answer
58 views

Does super position precede physical phenomena?

If a traveling wave has amplitude of d, it feels certain amount of force at that moment in time when it is displaced for equilibrium. Thus there is also strain on the string corresponding to that ...
VVC's user avatar
  • 434
1 vote
3 answers
3k views

How to prove the relativistic momentum? [duplicate]

As far as I know, the relativistic momentum of a particle is given by the equation: $$p=\frac{m_0v}{\sqrt{1-\frac{v^2}{c^2}}}$$ where $m_0$ is the mass of the particle and $v$ is the velocity of the ...
Display name's user avatar
0 votes
1 answer
91 views

The velocity of an object leaving the inclined plane

I saw the question below in our physics textbook. It asks A block of mass m is released and slides down on the frictionless inclined surface ( the inclined plane is of concrete and doesn't ...
ofenerci's user avatar
  • 221
0 votes
1 answer
51 views

Rotation of top of symmetries

while learning about rotation, I started to wonder what forces will come into play. Lets picture a top with two masses centered at (-1,0,-1) and (1,0,1) with rods connecting the masses directly to the ...
VVC's user avatar
  • 434
0 votes
2 answers
112 views

How is energy conserved in terms of "Work"

Basic equation of work is given by $F\cdot s$. When work is done, the energy is stored either in form of potential or kinetic. My question arises when we look at a case of applying $m g$ of force ...
VVC's user avatar
  • 434
0 votes
2 answers
76 views

When we can consider a body to be point sized?

In motion we idealize big object to be point sized. But we don't do it all the times. I am having some confusion on it. Please tell when we consider objects to be point sized?
user avatar
1 vote
2 answers
1k views

Relative velocities in Circular Motion

Recently I saw the following interesting problem Ann is sitting on the edge of a carousel that has a radius of 6 m and is rotating steadily. Bob is standing still on the ground at a point that is ...
Aditi's user avatar
  • 199
0 votes
0 answers
23 views

Quick question: can you describe the direction of motion relative to a particle?

In Gregory R.D.'s Classical Mechanics, he has written "Relative to a single particle, the only thing that can be specified is distance from that particle". My question is, isn't it possible to ...
PCeltide's user avatar
  • 101
0 votes
1 answer
771 views

Distance from ground to start suicide burn with initial height [closed]

In the figure below, the rocket is dropped with no initial velocity at a height of $h$. $d_f$ (free fall distance) is the distance in which the rocket is in free fall. $v_b$ is the velocity due to ...
dmoody256's user avatar
  • 103
0 votes
1 answer
114 views

Velocity of an object orbiting on a string

First, I'm sorry if this question is dumb, incoherent or vague - I never really studied any physics and this might be out of my grasp, but I tried to apply some of the math I know and figure these ...
John P's user avatar
  • 117
0 votes
2 answers
70 views

What is the direction of linear motion after this impact?

I've been thinking about a situation where I am not sure what the resulting motion would be. This is what I am thinking, 1) P is the point of application of force. If there are two force components ...
irobot96's user avatar
0 votes
1 answer
1k views

Finding tangential and normal velocity from a curve [closed]

How do you find tangential and normal velocity from a curve? I know how to find dy/dx, but I have no idea how to obtain ut and un and dv/dt.
Anastazia Nichole's user avatar
1 vote
3 answers
2k views

How is final velocity negative when acceleration is in positive direction?

When a body starts from rest and starts accelerating in positive direction and moves certain positive distance, its final velocity is given by : $$v^2 = u^2 + 2as$$ Solving it gives two values of $v$, ...
user68153's user avatar
4 votes
1 answer
186 views

Why is the kinetic energy a fixpoint of the Legendre transformation?

Question: Why is (from an intuitive standpoint) the kinetic energy $T$ a fixpoint of the Legendre transformation, i.e. $\frac{\partial T}{\partial \dot q}\dot q-T = T$ for any general coordinate $q$? ...
Stephan Kulla's user avatar
0 votes
1 answer
78 views

circular(ish) motion?

how would one describe as a function of time the position vector of an object with initial position $\vec{x_0}$ and velocity $\vec{ v_0}$ experiencing a central force of constant magnitude around the ...
user avatar
0 votes
1 answer
57 views

Change of variable in function

Suppose I have a function $h(\theta)$ measuring the height of a piston, with $\theta = \omega t$. I would like to know the vertical acceleration of this piston as $\omega$ changes at the point $\theta ...
Mikkel Rev's user avatar
  • 1,420
3 votes
2 answers
127 views

How to decelerate from velocity $v$ to stop time $t$ over distance $d$? [closed]

I'd be grateful for some help with this problem I am trying to solve. Let's say that I have an object travelling at a velocity $v$. I want that object to come to a halt in time $t$ AND travel exactly ...
the_ether's user avatar
0 votes
2 answers
232 views

Kinematics of particles

Do particles have to move in a straight line to apply Suvat equations? I always perceived that they do because acceleration can mean a change in the magnitude of velocity, a change in direction or a ...
The blank's user avatar
1 vote
2 answers
224 views

Why does wave keep on travelling despite destructive interference?

I've problem here. Imagine you've a line of spheres that are attached to each other with springs. You push one sphere down hard. it drags its neighbors down and which in turn pull their neighbors and ...
Muhammad Umer's user avatar
0 votes
1 answer
69 views

Confusion about valid set of virtual displacement

The answer of the problem below makes me confused about my thinking about virtual displacement... Consider the system in the figure below, similar to mechanisms used for aerial filming of sporting ...
XJY95's user avatar
  • 1
2 votes
1 answer
582 views

Motion equations for Woodpecker toy (multibody system)

I am trying to understand a rigid multibody model of a Woodpecker toy (see figure below). Now I am not going to go into details about the model or justify this approach, I am just trying to understand ...
SimpleProgrammer 's user avatar
-1 votes
1 answer
1k views

Why is the direction of net force on an object and the direction of acceleration of that object is different in this situation? [duplicate]

A $ 2.0 kg $ block is being pulled across a frictionless table by a rope with negligible mass at an angle $ \theta=60° $ (from positive direction of $ x $ axis, we have taken horizontal surface of ...
Mark fuxerbergstein6's user avatar
0 votes
2 answers
244 views

Why is the direction of net force on an object and the direction of acceleration of that object different in this problem?

A $ 2.0 kg $ box of cucumber extract is being pulled across a frictionless table by a rope at an angle $ \theta=60° $ (from positive direction of $ x $ axis, we have taken horizontal surface of table ...
Mark fuxerbergstein6's user avatar
0 votes
2 answers
15k views

The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than [closed]

The human body can survive an acceleration trauma incident (sudden stop) if the magnitude of the acceleration is less than 250 m/s². If you are in an auto- mobile accident with an initial speed of 105 ...
Daniel Bonilla Jaramillo's user avatar
1 vote
2 answers
414 views

Inconsistent Results with Momentum and Kinetic Energy

A speed skater with a mass of $m_1$ kg is moving at $v_{1i}$ m/s. He prepares to push the next speed skater of mass $m_2$ kg moving at $v_{2i}$ m/s. After the push, the velocity of the first skater ...
NM_'s user avatar
  • 121
1 vote
3 answers
1k views

If mass is doubled, how much more power is needed to sustain the same speed?

My problem involves an object completely immersed in a fluid, moving at some speed, using a certain amount of power to sustain that speed. It could be an airplane or a torpedo, among other things. (...
DrZ214's user avatar
  • 704
0 votes
1 answer
25 views

Kinematic Modelling with clockwise angles defined as positive

It seems when modeling a system for which an clockwise angles is defined as positive, the resulting equations become wrong. For example : In the picture below $\theta_x$, the orientation of the ball,...
ganto's user avatar
  • 103
1 vote
0 answers
54 views

How to accurate scale start velocity in projectile motions? [closed]

I have projectile motion where the angle $\alpha$ is $45^\circ$, and the start velocity is $45\ \rm{m/s}$. We can then expect it to land about $206.422\ \rm m$ away; however, if I were to change/...
Korg naw's user avatar
1 vote
1 answer
151 views

Angular velocity by velocities of 3 particles of the solid

Velocities of 3 particles of the solid, which don't lie on a single straight line, $V_1, V_2, V_3$ are given (as vector-functions). Radius-vectors $r_1, r_2$ from third particle to first and second ...
SilverLight's user avatar
1 vote
1 answer
343 views

Smoluchowski theory of Brownian Motion

I am studing Brownian motion, in particular I am reading the book "Brownian Motion, Fluctuation, Dynamics and Application" by Mazo. Now I am dealing with Smoluchowski theory, but I am having some ...
user502940's user avatar