All Questions
Tagged with kinematics speed
169 questions
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What is the velocity of ant? [closed]
My Approach:For any arbitrary motion of A and B, C must move in such a way that it forms a new equilateral triangle A'B'C'. Now how do I derive a relation between their displacement vectors so as to ...
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3
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257
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Where does speed and velocity differ? [duplicate]
I'm in Junior High and I still have some confusion towards speed and velocity. They sound like the same thing, where some object moves in a given direction, but there is a difference from both topics.
...
user298882
2
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1
answer
189
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Rotational motion from curved slope?
So I've learned for any slope with a sliding object, say a box, the speed at the bottom only depends on the height it was dropped from because of conservation of energy, assuming absence of friction ...
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0
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Visualisation tool for different speeds? [duplicate]
I'm a student often doing kinematics word problems with objects moving at X km/h, Y m/s, or Z cm/s. Yet, I have no idea what these units look like in real life.
Out of curiosity, I'm searching for a ...
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3
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Two values to the speed of light ...what does this mean in the real world?
If $E= mc^2$ then c = $\pm \sqrt{E/m}$. What is the real world meaning for a negative speed of light ? Anything traveling faster than $-300k m/s$ is travelling faster than the speed of light ? What ...
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What's the speed of the train with our point of reference being the person who's moving inside the train? [closed]
A person moving in a train with the speed of 1m/s to the right, while the train is moving in the same direction with the speed of 10m/s
From the person's point of view "considering that the ...
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2
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2
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41
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Estimation of greatest speed in a polyhedron
in order to control velocities in a three dimensional volume, I look for a proof or a proof idea for the following assumption:
Given a non-empty solid polyhedron in 3D, all points inside this set ...
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Is this intuition correct? (dot product)
So, it is based on the article below: Go to the bottom of the article where the 'Mario-Kart Speed Boost' example is.
So, the intuition in the examples makes sense to me but sometimes people explain ...
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2
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1
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267
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Is there a difference between instantaneous speed and the magnitude of instantaneous velocity?
Consider a particle that moves around the coordinate grid. After $t$ seconds, it has the position
$$
S(t)=(\cos t, \sin t) \quad 0 \leq t \leq \pi/2 \, .
$$
The particle traces a quarter arc of ...
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3
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2
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Need some help understanding velocity
I have just started learning kinematics and this is just a small question, that I wish for to clarified as it feels a little bit confusing. Below, the difference between speed and velocity is given. I ...
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What is the difference between two types of velocity?
What is the difference between $v=\frac{s}{\Delta t}$ and $\bar{v} =\frac{\Delta\bar{x}}{\Delta t}$, are they the same?
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Why do we need instantaneous speed?
I am new to this topic and was just wondering about the use of instantaneous speed. I mean, we use to calculate the speed of car let us say at 5 sec. So we take the distance travelled in 4.9 to 5.0 ...
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Term for travel time per distance
Does the physics community have a term for the time per travel distance, $dt/dx$? I.e. the reciprocal of the speed. Runners call this their pace.
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5
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Why is it said that speed always remains constant in circular motion?
One can cover circular motion with different speeds at different positions, right? The only aim is to complete his circular motion, right?
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How can speed be the magnitude of velocity
Say speed is the magnitude of velocity then:
\begin{align*}
v &=\left|\vec{v}\right|\\
\frac{D}{\Delta t} &= \left|\frac{\Delta \vec{x}}{\Delta t}\right|\\
\end{align*}
since $\Delta t$ is ...
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1
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Given a fixed average speed in the speed vs. distance graph, is it the fastest to travel constantly at that speed?
Is it true that among all the ways to travel a distance $X$ with an average speed $E$ in the speed vs. distance graph, traveling with a constant speed $E$ minimizes the time it takes to complete the ...
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Is instantaneous speed always equal to the magnitude of instantaneous velocity?
Is instantaneous speed always equal to the magnitude of instantaneous velocity? What about the infinitesimal time duration when the direction changes? How can it ALWAYS be equal?
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How is acceleration calculated when only the direction of velocity changes and the magnitude remains the same? [duplicate]
How is acceleration calculated when only the direction changes and the magnitude remains the same?
Guys, I know that my previous examples didn’t make sense and I’m sorry because I’m totally new to ...
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2
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What if the directions of the initial and final velocity are different in the conservation of mechanical energy equation?
I saw a problem, and saw that it could be easily solved using conservation of mechanical energy. So I wrote my equation:
$$mgh_1 + \frac12mu^2 = mgh_2 + \frac12mv^2$$
Where $u$ is initial velocity, $...
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340
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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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1
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How force affect the objects that we apply on? [duplicate]
Why do things get accelerated rather than do a moving at constant speed when we apply a force on them? How my force affect the object at atomic level? Does it increase the kinetic energy of atoms ? If ...
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2
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132
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Is there a physics law according to which, in general, the smaller an object is, the faster it moves? [closed]
I have always felt, in general, that dogs run faster than humans and that birds fly faster than dogs and than bees can fly or at least drift by the wind faster than birds and that plant seeds would ...
user256067
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Why do we experience more centripetal force when we make a sharp turn compared to a wide turn? [duplicate]
If $F=m\omega^2r$, why do we experience more force when we decrease the radius of the turn?
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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....
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2
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Would a speed camera register more speed if it moves in the opposite direction than the object it's measuring?
Earlier today, I was talking with my friend about speed cameras measuring different speeds when moving.
This is the situation:
I am the red car and I'm driving ...
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2
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3
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2k
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Velocity of a ball rebounding off a moving train
At the bottom of this page says (my emphasis):
It's interesting to note the speeds in the cartoon. The
propeller-beanie kid sees his tennis ball moving away from him at 30
miles per hour. So ...
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0
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Why are velocity and kinetic energy not proportional? [duplicate]
In the equation $E_k=\frac12mv^2$ the fact that the kinetic energy of a moving object is not proportional to it's velocity seems counter-intuitive to me.
Put another way, it seems intuitive to me ...
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3
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1k
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Why do we need concept of average velocity and average speed? [closed]
As I was thinking about average speed / velocity, I got curious, why do we need this concept. This average speed / velocity doesn't give accurate information about motion of an object then why it is ...
user238719
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3
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Why was the concept of velocity created? [closed]
Why do we use velocity instead of speed for different physics problems?
I recognize how they are different but why use one over the other?
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What is the difference between uniform velocity and constant velocity? [closed]
I think that uniform velocity implies constant speed but not constant direction. while constant velocity implies constant speed without any changes in direction.
Both tell us that there's no ...
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8
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The instant an accelerating object has zero speed, is it speeding up, slowing down, or neither?
This problem is from Khan Academy. Specifically for the blue point circled in red, the answer is that at this blue point, the object is neither speeding up nor slowing down. When I think about the ...
user225790
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7
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Is there centripetal acceleration with velocity of 5 m/s?
So if an object is moving at $5\ \mathrm{m\ s^{-1}}$ in a circle, is it accelerating?
Me and a friend are having a conversation about this.
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3
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680
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Speed and tangential acceleration in pendulum motion
Speed is a scalar quantity which corresponds to the magnitude of velocity, so it must always be nonnegative.
In a general 2d motion, the tangential component of acceleration is given by the time ...
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3
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154
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What is the best way to conceptualise a 'division' [closed]
This may seem like a strange question, but my question is more along the lines of trying to figure out how people were able to 'discover' the formulas which have shaped our understanding of the ...
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Effect on speed when decreasing the magnitude of acceleration
I'm struggling to come up with an answer to the following situation and question:
"Suppose you are driving your car along a straight road in the positive direction and are speeding up (increasing ...
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What would the position vs. time graph look like if the velocity vs. time graph was a curve?
In my physics class we are learning about velocity vs. time graphs and position vs. time graphs for an object. We have learned that if the object is moving with constant velocity (this would be a ...
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What would be the minimum velocity of a particle performing S.H.M.?
We were asked a simple question on a test:
What is the maximum and minimum velocity of a particle performing an SHM?
Note here that we're talking about a generic standard SHM here. If the maximum ...
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1
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258
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Are my observations about the differences between average velocity and speed, in 1 dimension, correct?
I've been struggling to understand the differences between average velocity and average speed in 1 dimension; by doing some exercises I think I have figured it out, but i want to check if I'm correct.
...
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2
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Rolling objects released from rest: time down the ramp [closed]
Since we are given the values of I for each object, I was able to calculate the KE's of each:
the solid spheres had KE of $1/5mv^2$; the hollow sphere had a KE of $1/5 mv^2$, and the hoop had $1/2mv^2$...
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4
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146
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How to express acceleration changing direction? [closed]
There is a ferris wheel that is rotating at a constant speed. Acceleration magnitude is zero. How do I put it in an equation?
$a=0$ or $\vec a=0$. If there is another way please tell.
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3
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Why speed = distance/time? [duplicate]
Is it merely an arbitrarily chosen definition that we created in order to quantitatively measure the speed of an object or is it some other way around. I want to know what's the reason behind such a ...
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2
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Can I equate 3.9 to 4 here or it's just completely wrong? [closed]
I have this question:
A particle moving in a straight line covers half the distance with speed 3m/s. The other half of the distance is covered in two equal time intervals with speed 4.5m/s and 7.5m/...
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If an object moves at constant speed, does it necessarily have constant velocity? [closed]
If an object moves at constant speed, does it necessarily have constant velocity?
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If two bodies move constantly but with different speed, do they move with acceleration relative to each other? [closed]
If two bodies move constantly but with different speed, do they move with acceleration relative to each other?
user205695
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Is there an agreed upon physics definition of the term 'speed'? For example, can it be negative?
The term speed is commonly defined as follows:
https://www.physicsclassroom.com/class/1DKin/Lesson-1/Scalars-and-Vectors
Speed, being a scalar quantity, is the rate at which an object covers ...
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8
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Why isn't average speed defined as the magnitude of average velocity?
Speed is usually defined as the magnitude of (instantaneous) velocity. So one could assume that average speed would be defined as the magnitude of average velocity. But instead it is defined as
$$s_{...
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2
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Calculating the Instantaneous speed
When we are calculating speed from the graph for a uniform motion the speed which get as an answer is actually the average speed and since in uniform motion the average speed is same as that of ...
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Can acceleration be both the "rate of increase of velocity" and the "rate of increase of speed" in Physics?
A Dictionary of Physics (Oxford University Press) defines acceleration as:
The rate of increase of speed or velocity
However, from reading many other definitions it seems to me that acceleration ...
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2
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368
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How instantaneous speed is defined as magnitude of instant velocity? [closed]
Let $s=$distance (a variable)
we define instantaneous speed = magnitude $\left[\frac{ds}{dt}\right]$.
However instantaneous speed is also defined as magnitude of instantaneous velocity
i.e. ...
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3
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Can speed vary within a given interval of uniform motion in a straight line?
The definition of 'Uniform motion' in a straight line says that the body covering equal distances in equal intervals of time is to be understood to be in uniform motion. However, can the speed vary ...
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