The description of the movement of bodies by their position, velocity, acceleration (and possibly higher time derivatives, such as, jerk) without concern for the underlying dynamics/forces/causes.

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Analysing kinetic energy in different frames [duplicate]

Case A: Say we observe a body X moving with a velocity of 30 on the +x and we(the observer) are stationary. Case B: The observer moves with a velocity of 50 on the -x. The body X is moving in the ...
-1
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0answers
22 views

Pls help me visualise this situation, I'm not able to understand it [on hold]

Find time of flight of projectile thrown horizontally with speed 50m/s from a long inclined plane which makes an angle theta= 45° from horizontal.
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0answers
38 views

Movement of a box containig a particle [on hold]

A small thought experiment: Imagine a rectangular box in space, containing particle, all resting at $t=0$ from your point of view. At some point in time $t>0$ the particle starts to move with ...
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0answers
21 views

Projectile motion and bouncing [on hold]

Prove that the number of bounces n after throwing an elastic ball on a frictionless surface with a known angle (j)relative to the horizon and the angle of the initial velocity is known also (k)..is ...
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1answer
28 views

projectile on an inclined plane [on hold]

Is the time of ascent equal to the time of descent? I tried it but I am not being able to prove it mathematically.
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1answer
38 views

I don't understand the approach used in solving this kinematics problem

The problem text is as follows: During the first half of a straight path, which is at $\alpha_1=60°$ relative to a reference line, a car is travelling at $v_1=72 km/h$. During the second half of the ...
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1answer
43 views

Differential velocity and acceleration [on hold]

A particle moves along the curve $X = 2\sin3t$, $Y = 2\cos 3t$, $Z= 8t$ How to find the velocity and acceleration when $t>0$?
8
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1answer
79 views

Can one rise through a free-falling rope?

I am a little confused about this question. I cannot imagine that it is possible to rise through a rope (assuming inextensible) that isn't fixed in its upper end. But when I solve this problem, I see ...
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3answers
43 views

Why is the sign of the tangential component of acceleration negative in this problem? [closed]

Since the train is slowing down at a constant velocity, shouldn't the acceleration equal zero? Why is it negative in this case?
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22 views

Pls solve this question of projectile motion [closed]

2 particles are projected one by one with same initial velocity from the same point on the ground, they follow same parabolic trajectory and are found to be in same horizontal level, separated by a ...
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4answers
180 views

Problems in the relation $a=v\frac{\mathrm{d}v}{\mathrm{d}x}$

We all know $a = \frac{\mathrm{d}v}{\mathrm{d}t}$. A little application of the chain rule leads to the relation $$a=v\frac{\mathrm{d}v}{\mathrm{d}x}$$ But the above equation shows that $a=0$ whenever $...
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1answer
42 views

Equation confusion regarding finding acceleration [closed]

Physics newbie here, sorry if this is super basic... I am learning about kinematic equations and am having difficulty reconciling two of the equations. Let's say I begin driving and after 1 second ...
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2answers
75 views

Circular Motion. Intuition on vectors as a physics interpretation [closed]

I am a maths undergraduate. I decided to start studying some basic physics trying to be rigorous with the math and uderstand the interpretations of some of the mathematical constructs and see how ...
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2answers
54 views

If change in position over time is average velocity, why doesn't change in position over time squared equal average acceleration?

For example, let's say a car is experiencing an acceleration of $1$m/s$^2$, for $6$ seconds so it goes $18$m. Now the average velocity is found through dividing $18$m by $6$s which is in line with the ...
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1answer
24 views

How to estimate the relative motion using kinematic equations?

Background I am reading the following thesis: Todosiev, E.P., 1963. The action point model of the driver-vehicle system. On page 9 it describes the relative motion between 2 cars as follows:...
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0answers
31 views

Does this calculation give displacement or distance?

So we have velocity as a function of time given $\overrightarrow{v}(t)=(1-2bt)k\overrightarrow{r_0}$ where $b,k$ are positive constants and $\overrightarrow{r_0}$ is a unit vector. It is found that if ...
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2answers
36 views

Is the magnitude and direction of gravity on an object the same as the objects vertical velocity?

I need to make a diagram for an entry level college physics class. I need to show the magnitude and direction of gravity on a flying object and also show the magnitude and direction of the objects ...
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1answer
61 views

Position / velocity / acceleration vs time graphs when falling towards a black hole

In Newtonian physics, as far as I understand it, for a small object falling towards a massive object, the graphs of position, speed and acceleration vs time look like this: (If the massive object ...
6
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1answer
117 views

Why doesn't the relativistic formula for momentum appear consistent with collisions?

The relativistic formula for momentum is $$p = \frac{mv}{\sqrt{1 - \dfrac{v^2}{c^2}}} \,.$$ In the following example, I apply the formula in the most basic way possible to the addition of velocities. ...
0
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1answer
68 views

Projectile motion on an inclined plane [closed]

Two parallel straight lines are inclined to the horizontal at angle $\theta$. A particle is projected from a point midway between them so as to graze one of the lines and strikes the other at a right ...
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0answers
33 views

Contradictory kinematics formula [duplicate]

The displacement of a particle in the $t$th second of its motion is given by: $$ S(t)=u + \frac{a}{2}\left(2t-1\right) $$ where $u$ is the initial velocity, $a$ is the acceleration and $s$ is the ...
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1answer
23 views

Find the initial velocity's angle of a projectile knowing only the ratio between the horizontal distance traveled and max height

The ratio between the horizontal distance traveled and the launch height is 3 to 1. I think it is possible to find the angle given this information, but how exactly do you do it? I think it's arctan(2/...
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1answer
79 views

What happens if you fly a drone inside moving passenger airplane? [duplicate]

I have a little question. If I mark an X in the center of a passenger airplane, and try to fly a drone from the X mark in the moving passenger airplane (800-900 km/h), what will happen to the drone? ...
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1answer
50 views

Defining Uniform Motion

According to Wikipedia the definition of motion is: In physics, motion is a change in position of an object with respect to time. Motion is typically described in terms of displacement, distance, ...
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1answer
58 views

Projectile question doubt [closed]

A hunter wants to shoot a monkey with an arrow by launching the arrow at a speed $v_0$ at a distance of $L$ from the base of a tree of height $H$ on which the monkey is sitting. Now on watching the ...
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2answers
50 views

Simple change in velocity question

The hand of a clock is 1cm long. find the change in velocity of the hand in 15 seconds. The question is pretty simple, $v=2\pi R/T$ and then using the vector addition one can easily get answer which ...
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1answer
1k views

Is running in a zigzag helpful in avoiding being shot by an arrow? [closed]

Two people A and B start at a certain point. B runs away from A to another point. A shoots arrows at B. Is it helpful for A to run in a zigzag rather than in a constant direction? To be more ...
3
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0answers
54 views

Branching ratio for a bound state

Consider the meson $\Upsilon(10860)$. It decays into $B\bar{B}$, $B\bar{B}^*+cc$ and $B^*\bar{B}^*$. The mass of $B$ is $5.28 ~\textrm{ GeV}$ and mass of $B^*$ is $5.33~\textrm{ GeV}$. The branching ...
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2answers
85 views

Solar Sail Questions

I'm just looking for a good (better) analogy. How do massless photons put pressure on a surface especially when it's a mirror? Using the analogy of the wind (atmosphere) on a sail breaks down when I ...
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2answers
51 views

Point object, Kinematics

I am very new to physics. This evening, I was reading about the concept of objects to be considered as point objects under some circumstances. And I was trying to think of circumstances under which ...
0
votes
1answer
70 views

How do you arrive at this equation? $ \bar{v} = v_2 - \tfrac{1}{2} a \Delta t $

$$ \bar{v} = v_2 - \tfrac{1}{2} a \Delta t $$ $\bar{v}$ being average velocity and $v_2$ instantaneous velocity at one point this equation was used to find instantaneous velocity from average ...
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2answers
39 views

Acceleration velocity relation

I just happened to come across this specific question in physics:- Q: If a particle is moving along a straight line with increasing speed, then, (1) its acceleration is negative (2) its ...
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1answer
66 views

Why does $k^z/E$ have dimensions of inverse velocity rather than velocity?

I'm studying quantum field theory and I want to prove the cross section. In Peskin's book, equation 4.77 says that: $$ \frac{1}{\left | \frac{k_{A}^{z}}{E_{A}}-\frac{k_{B}^{z}}{E_{B}}\right |}=\frac{...
0
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1answer
33 views

Area under the displacement-time graph giving time?

This is probably very stupid, but today at a lecture, our professor solved a problem where we had to find the time taken to travel from 0-5m, where $v = 3/x$ (velocity is a function of position.) ...
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1answer
29 views

Velocity ; Acceleration [closed]

A ball was thrown vertically upwards with a speed of 3m/s. The ball reached a highest point before falling down to the ground. What is the acceleration of the ball at the highest point? A 0m/s2 B ...
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4answers
89 views

Explain $\Delta x = v_0t + \tfrac{1}{2}gt^2$ please? [duplicate]

$g = \Delta v/t$, so $\Delta v = gt$. $v = v_0 + \Delta v$, so $v = v_0 + gt$. So if $\Delta x = vt$, then $\Delta x$ should be $v_0t + gt$. Why the $\tfrac{1}{2}gt^2$? I'm really confused, so this ...
0
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1answer
33 views

Acceleration at rest when ball is thown [duplicate]

If a ball is thrown vertically upward and it comes to rest for a moment, then its velocity decreases and becomes zero. Does its acceleration also becomes zero? If yes then how ball falls down?
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2answers
53 views

Can a system's internal forces change the system's motion?

Let say the motor makes the two rigid body rotate as a same velocity. (they rotate the opposite direction) then the Net force of the motor is 2Fsin(Theta). The acceleration of the motor is 2Fsin(theta)...
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4answers
56 views

Area under and slope of the motion graphs

I wanted to ask in general what area under the graph means. Also which physical quantity is highlighted by area under distance vs time graph. I'm confused that area is a 2 dimensional concept and it ...
-1
votes
3answers
60 views

How to solve this one dimensional motion question? [closed]

I was able to deduce the following information from the problem: acceleration of police = 2m/s^2 x0 = 50 meters t= 5 seconds final velocity = 0 m/s However, I'm not sure what to do next.
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2answers
57 views

Finding if two objects collide

The question that I'm trying to understand is this: This is the part of the solution I don't understand: From my knowledge, if $v_p-v_q$ is due south, this means $r_p-r_q$ is also due south, ...
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0answers
57 views

Physical pendulum dynamics confusion

I'm validating a Matlab Simulink SimMechanics model analytically. The model consists of a physical pendulum (uniform rod with length $l$ and width $w$) which is torque driven. I'm somewhat confused ...
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votes
1answer
49 views

How would you go about solving this tricky distance problem? [closed]

I've tried calculating the distance the runner has left to get to the finish line by the time the bird gets there and adding it to the distance the bird has to fly back to the runner. Then I ...
-1
votes
1answer
69 views

Considering velocity-distance graph [closed]

A car is travelling at constant velocity. Its brakes are then applied, causing uniform deceleration. Which graph shows the variation with distance s of the velocity v of the car? The solution is A, ...
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votes
2answers
51 views

How to calculate initial acceleration of a projectile motion? [closed]

I have an object following a projectile motion, that hasn't got horizontal acceleration but only vertical -g. What is the acceleration that I have to use in the second law of motion (F = ma) in order ...
0
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2answers
52 views

Finding the height of a balloon [closed]

A balloon moves up vertically such that if a stone is thrown from it with horizontal velocity $u$ relative to it, the stone always hits the ground at a fixed point $ 2u^2/g$ horizontally away from it. ...
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2answers
46 views

How exactly do objects move

Suppose I have a piece of steel that is made up of one row of 100 atoms. Now, suppose I try to slide it across a surface by pushing it forward, the atom I come into contact with (the last atom in the ...
0
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1answer
28 views

Equations of motion acceleration doubt

So i was going through some text today morning. Where it said $$ a = \frac{vdv}{dx} $$ So they then went on to, $$ vdv = adx \\ \implies \int vdv = \int adx$$ But,I am very certain acceleration is ...
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3answers
47 views

Equations of motion derivation doubt

I just started on learning how to derive the equations of motion using calculus. This is my first time and I have a basic doubt. So $v = \large{\frac{dx}{dt}}$ Then, $dx = v dt $ What does this ...
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2answers
86 views

Components of Velocity in polar co-ordinates

Consider a point moving along a curve in a plane. The position of a point P on a coordinate system can be specified by a single vector $\vec{r}$=$r\hat{r}$. A rough sketch describing the situation is ...