All Questions
Tagged with kinematics speed
169 questions
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How do I find the instantaneous velocity in real life? [closed]
I am learning about Instantaneous speed and velocity in Khan Academy. I understand the concept and calculation, but how do I know the different instantaneous speed at different points in real life?
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5
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What's wrong with this argument that kinetic energy goes as $v$ rather than $v^2$? [duplicate]
Trying to non-technically explain why (kinetic) energy goes as $v^2$ rather then the perhaps-more-intuitive "double the speed, double the energy" $v$, I ended up putting my foot in my mouth (itself a ...
user89220
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Tangential Velocity - vs - Tangential Speed
It's the first time for me to ask a question here.
Is there a difference between "Tangential Speed" and "Tangential Velocity"?
As far as I know, Speed is scalar quantity defined only with its ...
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How do I know my speed in this time interval?
I am reading a book on trigonometry and the next chapter is named 'Linear and Angular speeds'.So I started to think about linear speed.
I thought that I could drive a bicycle in $2$ ways.
Either I can ...
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1
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Definition of speed [duplicate]
Is speed the magnitude of the velocity vector or the travel distance divided by the travel time?
A common example shows the problem: circular motion. "When something moves in a circular path (at a ...
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1D Motion homework
A helicopter is ascending vertically with a speed of 4.00 m/s. At a height of 125 m above the Earth, a package is dropped from a window. How much time does it take for the package to reach the ground? ...
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two balls thrown upward at the same time
Ball A is thrown upward at the same time as ball B and with half the speed of ball B. a) Will ball A or B hit the ground faster? b) How much higher does B go than A?
This is one of my homework ...
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Speed in min/km given distance in meters and time in seconds
How to calculate speed in min/km given distance in meters and time seconds? I used formula v = d/tbut having problems converting units.
I've tried ...
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6
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Why is speed defined like it is?
I have a rather basic, maybe even dumb, question. I was wondering why speed is defined as it is:
$s = d/t$
Of course, what the equation means is not too difficult to understand. However, there are ...
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4
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Body in uniform motion
A body is said to be in uniform motion when it covers equal distances within equal time intervals. So that means at constant speed. However constant velocity also seems to be correct. So if one is ...
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What is the difference between $d|v|/dt $ and $ |dv/dt| $ & between $d|x|/dt $ and $|dx/dt| $? [closed]
Here, $v$ represents velocity vector and $a$ represents acceleration vector.
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Is value of speed equal to the magnitude of velocity?
For example: - suppose a body covers a semi-circle in $5$ seconds, then distance$=\pi * r$, where $r$ is the radius of the semi-circle. Displacement is $2r$ only. Then the value of speed is $[\pi * r] ...
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Why doesn't this formula work? [duplicate]
Let's assume that an object has KE expressed by velocity $v$ and mass $m$.
If work $w$ has been done to this object such that its new speed (same direction) is $s$. There are 2 ways(I know) to ...
user154674
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2
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How do you find the speed of an object knowing the co-ordinates in $\mathbb{R}^3$ e.g. (2, 3, 4)? [closed]
How do you find the speed of an object knowing the co-ordinates in $\mathbb{R}^3$ e.g. (2, 3, 4)?
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Calculate the distance traveled when "braking" for fixed amount of time to a fixed velocity [closed]
I have the problem that I need to know how many steps I traveled when I go from velocity $a$ to $b$ in a fixed amount of time. I always know how long it will take me to go from velocity $a$ to ...
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Is the term "deceleration" ambiguous? Does it refer to negative acceleration, or is it something else entirely? [closed]
What does that term truly mean? Sometimes it confuses me what exactly it refers to.
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How does instantaneous speed work for circular motion?
Why do we use the formula $\lim_{\delta t→0} \delta s/\delta t$ to get the instantaneous speed? Since speed is distance divided by time, what does the limit have to do with this? I have a very limited ...
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Is centripetal acceleration based on speed or velocity?
I know that the formula for centripetal acceleration is $\ a_c = v^2/r$.
Does the $v$ represent the average velocity of the car which is the arc length traveled divided by the time? If the answer is ...
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Why does centripetal acceleration have a magnitude?
Assuming that the magnitude of velocity is constant. Why does centripetal acceleration have a magnitude? Since acceleration is the rate of change for velocity and its magnitude remains the same ...
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2
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Magnitude of instantaneous velocity vs speed
Magnitude of instantaneous velocity = $|dr/dt|$ but this is not always equal to $ds/dt$ where ds is the infinitesimally small change in distance in the interval $dt$
Which one is speed?
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Question about $a = v\ \mathrm dv/\mathrm dx$
Consider $\vec{v}$ Now differentiating this w.r.t time,
$$\vec{a} = d/dt( \vec{v}) = \vec{v}(d\vec{v}/dx)$$
Now this multiplication of vectors obviously makes no sense. This along with the fact that ...
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2
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Can a solid object gain speed instantly?
Is it possible for a solid real world object to instantly gain speed without having to accelerate from $v = 0 \, \text{m/s}$ to $v = 1000\,\text{m/s}$, or does it have to accelerate in order to reach ...
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What is really instantaneous?
How can a body travel at an instant and what does instantaneous speed tells us?
What really is meant by speed of an object at an instant if an object does not travel at an instant? I would like a ...
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How far from the starting point do the pieces fall on ground [closed]
An object is thrown with speed 20 m/Sunder the angle pi/3 rad with the horisontal direction. In the highest point, the object is divised into two pieces with same weights. One of them, after the ...
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Constant acceleration of an object [closed]
Why when an object keeps moving at a constant acceleration, it's speed is not always greater than 0?
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3
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Does Kinetic Energy assume constant acceleration?
Okay, I've always been someone who doesn't learn anything unless I can prove it. In this case, I set out to prove the Kinetic Energy formula and (wrongly?) found that it was based on constant ...
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Why do we care about the difference between speed and velocity?
I teach 7th grade students about the difference between speed and velocity. One of them ask me why do physicists create the concept of velocity. I cannot answer. I don't know precisely why do we care ...
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How did we arrive that kinetic energy $KE = \frac{1}2 mv^2 $? [duplicate]
There are proofs mathematically how we get kinematics formulae. But i can't understand the proof for kinetic energy equation. I know we can proof $KE$ equation from work energy theorem but what I ...
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Is there any proof about mathematical definition of constant speed agreeing with intuition?
First, I wanna clarify that I understand the intuition behind the definition of velocity in 1, 2 and 3-D (The derivative of the position vector).
But the other day I was thinking if that definition ...
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What is meant by negative direction of velocity? [duplicate]
What is negative velocity and negative direction of the velocity?
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Can velocity be negative? [closed]
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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Can motion be characterized without time as independent variable? [closed]
I was just thinking about speed = distance/time which relatively describes how fast something is moving wrt some still object.
So if by some wishful thinking or some coordinate system I remove the ...
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1
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How fast does a long object bent at the center need to be travelling in order to boomerang?
At an angle, of course.
Standard pressure, average temperature, and calm wind.
Bonus question: Can an object that is not bent boomerang at all? If yes, how different would the equations for this ...
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Another view on mass energy equivalence? $ E = m_0 c^2 [1 - \sqrt{1 - (v/c)^2}]$? [closed]
(this is old thread, but i have edited this question to be more brief)
In the paper, http://arxiv.org/pdf/physics/0206061.pdf "Fundamental Disagreement of Wave Mechanics with Relativity", ...
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3
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Initial speed in homework problem [closed]
This is a homework question. I tried to solve it, but failed.
I had to translate this question, so please forgive me if it is poorly worded.
In this question you can ignore the atmospheric ...
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Angular speed and normal speed
The instantaneous speed of a point along a circular path is given by $v=\omega r$, where $$\omega = \frac{\Delta \theta}{\Delta t},$$ $s=\Delta \theta r$, and $v=s/t$.
However, isn’t the displacement ...
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Explanation about friction force directions of two moving bodies in contact
can someone explain me why in this scenario (picture below) we have a friction force Ftr12 in the same direction as movement (left part of the picture, case 1 ) and how these directions of friction ...
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Calculate constant acceleration for a length of track with start at rest and final velocity known [closed]
My maths and physics are rusty... I'm a bit ashamed, but I have this problem:
Let's have a 1000m linear accelerator (mass driver) propel a payload at constant acceleration, with a final velocity of ...
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Change of direction in physics when an object in motion stops
Consider an object moving with an acceleration $a = -1 \text{m/s}^2$ starting with speed $v(0) = 4 \text{m/s}$ towards east and stopped after 4 seconds.
(There are no friction.)
After 4 seconds, the ...
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1
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Moving objects along a radius
I'm working on a project involving a Roomba which I'd like to move precisely from coordinate to coordinate. To move the Roomba manually you need to give it a velocity between -500 to 500mm/s and a ...
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1
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Kinetic Energy - use a log scale or not? [closed]
Lets say we have a series of balls and an eggs. All items have equal mass but are traveling at different velocities.
Thus they have differing kinetic energies.
Now, for each 'ball' object we have, ...
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Why can velocity and acceleration be negative?
Why is speed and acceleration negative when $V_1$ of an object is say 150m/s, $V_2$ is 0 m/s and $\Delta d=0.50\,\rm m$? I found the time it takes which is 0.0033s and the acceleration to be 90909.09 ...
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Calculating Kryptonian speed in the movie "Man of Steel"
This is my first question, so I'm not sure if this is the right place to ask but:
How would you go about calculating the speed of Kryptonians in the movie Man of Steel (2013)?
Specifically, I'm ...
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In Which Position A Co-passanger should Sit On A Turning Bike
Pardon me for this very basic mechanical science question. But I just want to clear my doubt it. Whenever I sit a behind someone on a bike I get confused when the the bike has to take a sharp turn.
I ...
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Does my (too low) tire pressure, affect the speedometer of my car?
Does my (too low) tire pressure, affect the speedometer of my car?
How big is this effect?
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Difference between Speed and Velocity
What is the difference between Speed, Velocity and Acceleration? Could any one describe it pictorially?. I am more over confused even after investigating many times. I am unable to relate myself ...
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1
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Find the average speed and velocity of the object [closed]
An object travels 11 m north and then turns around and travels 25 m south. If the total time of travel is 52 s what is the average speed and velocity of the object.
I used the formula I was told
...
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1
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How do you find the average speed and average velocity? [closed]
The shuttle craft "Galileo" travels at a constant velocity of $2.73*10^3$ m/s up for $34.0$ min. and then turns around to travel $1.45*10^3$ m/s down for $15.0$ min.
a) Find its average speed.
b) ...
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Kinematics - Concept of average velocity [closed]
Average velocity, as I have heard, cannot be found simply by finding the average of two numbers. I have a question on average velocity, but am simply unable to proceed:
A particle moving in a ...
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Is there any significance to the negative sign on this speed?
A girl is riding a bicycle along a straight road at constant speed, and passes a friend standing at a bus stop (event #$1$). At a time of $60$ s later the friend catches a bus (event #$2$)
If the ...
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