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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2answers
51 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 ...
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1answer
22 views

Radial and angular coordinates of a route? [on hold]

Certain bug has the route described by the radial coordinate $r(t)=\frac{at²e^{-bt}}{1+t²}$, where $t$ is in minutes, and the angular coordinate $\theta(t)=b+ct²$ in radians. Consider $a$,$b$, and ...
3
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3answers
1k views

Negative vectors (e.g. velocity)

If you said someone had a velocity of $-12\,{\rm mph}$ and they were traveling north? Wouldn't it mean that they were traveling $12\,{\rm mph}$ south? This is a quote from here: if something ...
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0answers
24 views

Equation of distance for two racing cars? [on hold]

Two cars were racing along a straight track namely CAR A and CAR B. They both started from same starting point with initial velocities $ v_1 $ and $ v_2 $ and constant acceleration $ a_1 $ and $ a_2 $ ...
-3
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0answers
24 views

Travel time in combined driving/walking trip [on hold]

A car is sent to take a student from coaching every day. The car arrives at the coaching 15min before the time. One day coaching gets closed one hour before the usual time. Then the student without ...
25
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5answers
6k views

How does a mobile phone vibrate without any external force?

How does a mobile phone vibrate without any external force? By Newton's law, any body can't move without any external force
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2answers
44 views

Motion on Escalator [on hold]

A and B step onto a escalator going from floor 1 to floor 2 simultaneously. A takes two steps forward and one step backward, whereas, B takes one step forward and two steps backward. Both move with ...
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3answers
6k views

What is displacement? Position relative to a reference point or change of position

What is the "official" or most useful definition of displacement in the context of kinematics? There are two common ones: Displacement is the length and direction of a line from a fixed reference ...
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0answers
27 views

Average velocity from instantaneous velocity-time function [on hold]

The instantaneous velocity v of a particle at any time $t$ is given by $$v= 4t^3-2t+1$$ where $t$ is in sec and $v$ is in cm/s Find the average velocity of a particle during 3rd second.
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2answers
229 views

Projectile motion - calculate landing angle

A projectile is launched at a $45^\circ$ angle, aiming for a target at a distance of 15 feet away from, and $2$ feet below the starting position. I'm looking for equations to determine: The ...
-3
votes
0answers
19 views

percentage increase in velocity to win a race [on hold]

In a race for $100\ \mathrm m$ dash,the first and second runners have a gap of half meter at the midway stage. By what percentage should the second runner increase his speed just to win the race?
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1answer
237 views

Inclined plane, circular motion and the friction

Suppose we have a cylinder on an inclined plane of mass $m$ and radius $R$ moving without sliding (so that $\varepsilon = a/R$). Why is the friction $F$ causing the circular motion sometimes lower ...
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1answer
44 views

Can velocity be negative? [on hold]

In free fall I use the formula V=g*t and g is negative(-9.8m/s^2). It gives me negative.
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0answers
34 views

Particle Under Constant Acceleration Problem [on hold]

A car travelling at a constant speed of $45.0\:\mathrm{m/s}$ passes a trooper on a motorcycle hidden behind a billboard. One second after the speeding car passes the billboard, the trooper sets out ...
-2
votes
1answer
29 views

Dropping a bolt in an accelerated lift [on hold]

Here's the problem given to me: A lift starts from rest with an acceleration of $a$. At the time it starts, a bolt is dropped from the top of the lift. If the height of the lift is $h$, find ...
0
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1answer
40 views

Derivation of centripetal acceleration

While reading HC Verma chapter 7 circular motion I came across a derivation which I couldnt understand. I have marked my doubt with red. I don't understand from where +dw/dt [- i sine +j cos0] came ...
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0answers
13 views

Finding $x$ and $y$ component of a dog running [closed]

I'm new to physics and cant get through this problem atm... A dog running in an open field has components of velocity vx = 3.5 m/s and vy = -1.4 m/s at time t1 = 10.3 s . For the time interval from ...
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1answer
39 views

If two cars have the same acceleration at time $t$, are the velocities of the cars the same at time $t$?

So when I look at the question logically, I reason that if I had two cars: Range Rover and BMW, at time t, I could pump the gas and make them accelerate at the same rate at 0.5 m/s^2 but I could be ...
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0answers
63 views

What does $dx/dt$ mean in this formula? [closed]

The formula i'm struggling with is A1a in the appendix of this paper (A double pendulum model of tennis strokes. Rod Cross, University of Sydney. 2006) - LINK. I understand all the other terms of the ...
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2answers
370 views

Ball flying towards me - Newton's third law is violated?

I was trying to answer the question of the flying ball here on the basis of Newton's third law and momentum conservation. Here is what I have tried. Lets take a ball mass of $m_1$ (index 1 is the ...
3
votes
2answers
87 views

Watching Airplanes Fly Toward You

Recently, I was enjoying the stars on a cool summer night and saw an airplane flying toward me from the distance. I observed its path as it started out as a small dot in the distance until it flew ...
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0answers
71 views

Question about speed riddle and relativity [closed]

My father posed to me the following riddle. suppose there was a 2 mile stretch and you wanted to average 60mph. You went the first mile at 30 mph assuming instentanious acceleration how fast do you ...
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1answer
36 views

Finding Velocity from Acceleration [on hold]

I have an Acceleration signal (from accelerometer) for a bat that hits a ball. Is it possible to obtain the Velocity of the bat and the ball with just the acceleration signal? My intuition obviously ...
3
votes
1answer
185 views

General motion of a cone on an inclined surface

Suppose that a solid cone is placed horizontally on an inclined surface and is initially at rest. How will the cone move when it starts motion due to its weight? I know that its motion depends on the ...
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0answers
34 views

Moves without acceleration [closed]

The distance between boat A and boat B is a. Two boats move with no accelaretion with speed =v from two direction. Boat A moves in direction of the line which is perpendicular to the lakeshore while ...
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0answers
18 views

Two particles of different velocities travel through a region of time-dependant acceleration. At what time do they meet afterwards? [closed]

Two projectiles: $P_{1}$ and $P_{2}$ have velocities $v_{1}$ and $v_{2}$, both propagting in the x direction and starting at $x=0$. They propagate with constant velocity over a distance $L$ and reach ...
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2answers
49 views

Calculating acceleration via differentiation of velocity [closed]

I am just starting with calculus and kinematics. I saw this particular question: The velocity of a particle at a distance $x$ is given by $v^2 = 4\cdot (x \sin (x) + \cos (x))$. Find the ...
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0answers
20 views

kinematic constraint of spacecraft

I am now reading a paper about trying to use convex optimization to solve the attitude control of spacecraft. However, I do not have background on the physical part: Let 1. $\omega(t) = ...
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2answers
237 views

How to find Tangential/Radial/Angular Velocity for motion in any curve?

Is the radial velocity responsible only for changing distance between objects and the component perpendicular to it only for change in direction? If so why? Please try to give a different explanation ...
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1answer
32 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: $$\mathbf{r_A}=\begin{pmatrix}r_{A_{x}}\\r_{A_{y}}\\r_{A_{z}}\end{pmatrix}$$ ...
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2answers
41 views

Is distance considered only for objects which have already moved?

I have this confusion concerning distance and speed. Typically, we express displacement and distance relative to a reference point, which we regard to be an unmoving location. As displacement has a ...
-3
votes
2answers
76 views

Use equations to create a realistic problem [closed]

Given the following equations: $100$ m = $0$ m + ($50 \cos\theta$ m/s)$t_1$ $0$ m = $0$ m + ($50 \sin\theta$ m/s)$t_1$ - $\frac{1}{2}(9.80$ m/s2$) t_1^2$ I am supposed to make up/create a real-life ...
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5answers
74 views

How can I find initial and final velocity? [closed]

Is there a way to find initial and final velocity if I only know the acceleration and distance and which formula must I use? I do not know the time either. EDIT Thank you for all your answers! You ...
3
votes
3answers
7k views

Finding the max height of a ball launched as a projectile using work-energy

A ball is launched as a projectile with initial speed $v$ at an angle $\theta$ above the horizontal. Using conservation of energy, find the maximum height $h_\text{max}$ of the ball's flight. Express ...
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2answers
51 views

Finding acceleration due to gravity of a 2D projectile

Can I find acceleration due to gravity of a 2D projectile given only the peak of the projectile, the point of impact, initial angle, and initial velocity? Specifically what is missing is the initial ...
0
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2answers
71 views

Average acceleration: why I am getting different results?

Let's consider a simple school problem. A car starts moving during 3 seconds with a constant acceleration of 1 m/s^2. Then it stops accelerating and moves 3 seconds more with a constant speed. Find ...
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1answer
43 views

Time traveled assuming instant acceleration/decelaration

I am working on sort of a motion planning algorithm where I need to estimate the time it takes to travel along a certain path of points (straight lines between consecutive points, i.e I am assuming ...
8
votes
1answer
369 views

Is it possible to determine particles' velocities from their crossings on a ring?

2 particles are constrained to move in a ring. Both particles begin moving at $t=0$ from $p=0$, each particle moving in the opposite direction of the other. It is known that they are moving at ...
3
votes
2answers
59 views

Best way of calculating average acceleration in lab experiments

I am doing a lab experiment that works as follows. An object moves along the $x$ axis with an initial acceleration and then moves with a pretty constant velocity that may slightly vary within $20\%$ ...
0
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1answer
50 views

Would displacement vs time of circular motion be a sin/cos curve or parabola

If you were to graph the displacement from one specific point in a circle of an object rotating, example the boomerangs displacement from the thrower. Would you use a parabola, since in a cos/sin ...
1
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0answers
36 views

When this CD is spun so fast that it shatters, why does the warped shape move slower than the surface?

In this video where a CD is spun abnormally fast to the point of shattering, one notices from the writing on the CD that the surface is spinning faster than the warp "shape" is. In other words, the ...
1
vote
1answer
39 views

Intuitive picture for Mandelstam $t$

In tree-level electron-positron scattering one has two possible channels corresponding to Mandelstam variables $s$ and $t$. The $s$-channel ist fine, there $\sqrt s$ is just the center of mass energy ...
1
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1answer
128 views

In perfect vacuum (no external force), if I apply a small amount of force to a body, will it continue to accelerate forever?

According to the equation F = ma, the greater the force applied to a body, the more is it's acceleration. But in a place where there is no gravity or any other kind of external force, If I apply a ...
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votes
0answers
19 views

Particle interaction kinematics in lab frame

Attempting a question from a past paper on scattering kinematics, fixed particle mass $m$ is struck by another particle mass $m$ with kinetic energy $T$. By evaluating $s$, $t$ and $u$, and their sum ...
1
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2answers
70 views

Doubt on series springs [closed]

Here is a description of the motion of two springs in series. The premise is that the force on the two springs is the same. This is derived from the following reasoning: when I pull the mass with a ...
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2answers
94 views

I don't understand the formula of constant deceleration required to prevent a vehicle collision

As I was looking for the formula that an Intelligent Speed Assist technology use to calculate the required deceleration that a vehicle must apply avoid collision, I found this one: $$a = \frac{V^2_0 ...
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votes
3answers
1k views

Speed of an object in air versus in vacuum

Okay, imagine that you are shooting a rocket down a tunnel that is 60 miles long and the rocket is travelling at 60mph, so the rocket should reach the end of the tunnel in a hour, right? Yep, in an ...
0
votes
1answer
129 views

Find constant acceleration needed to reach point (possibly related to projectile motion on slopes) [closed]

Given a particle with a position $p_0$ and an initial velocity $\vec{v_0}$, what acceleration $\vec{a}$ do we need to reach point $p_1$ and how long until we have reached $p_1$? The magnitude of the ...
1
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1answer
60 views

Why does everything written on a page appear in concentric circles when we rotate that page? [closed]

When i put a pencil in the middle of a paper and rotate it very fast, whatsoever is written on it, will appear in concentric circles. What is the reason behind this phenomenon and what is it called?
8
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5answers
16k views

Why does work equal force times distance?

My 'government-issued' book literally says: Energy is the capacity to do work and work is the product of net force and the 1-dimensional distance it made a body travel while constantly affecting ...