All Questions
13 questions
-1
votes
1
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110
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Speed is equal to distance divided by time but is this correct?
In this study https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9784821/, the distance the punch travelled from start to impact is 0.49 meters and the time taken from start of punch (that's it, they define ...
- 364
1
vote
2
answers
142
views
Average velocity showing different results
I was solving a question, in which, a particle has travelled a distance $s$, with initial velocity $0$ and constant acceleration.
So the equation of motion becomes,
$$ v = a t \tag{1} $$
and
$$ v = \...
- 56
-1
votes
1
answer
228
views
What does instantaneous velocity mean? [duplicate]
What does instantaneous velocity mean?
on google it says "Instantaneous means something happens very quickly, in a single moment. It's similar to the meaning of "instant", but most ...
- 1
1
vote
5
answers
207
views
Speed and Velocity
Why did physicists develop the concept of velocity? I searched on the web, but I didn't get a satisfactory answer. All I got is that velocity has a direction whereas speed does not. Why do we need ...
- 19
3
votes
3
answers
151
views
Can $d/t =$ speed ever be wrong? Is there a more accurate way to determine speed?
Is there a more accurate way to determine speed? I am asking because this has to do with an accident reconstruction where my son was killed.
The investigators are trying to conclude his speed prior to ...
1
vote
1
answer
94
views
Simple difference between module of velocity and time derivative of module of position [duplicate]
What is the conceptually difference between the two:
$$\frac{d|\vec{r}|}{dt}=\frac{\vec{r}\cdot\frac{d\vec{r}}{dt}}{|\vec{r}|}\neq|\dot{\vec{r}}|\equiv \bigg|\frac{d\vec{r}}{dt}\bigg|$$ ...
- 189
0
votes
1
answer
41
views
What is displacement time graph for this object which is in $xy$ plane going in sine wave like path from A to B. Also can velocity constant in path?
The path is from A to B in sine wave curve while the displacement is straight line.So how displacement is calculated for graph purpose here
1
vote
1
answer
333
views
Distance given two velocities
I have a home trainer that is connected to an application that I am writing which needs to calculate a distance traveled given the speeds that the trainer is sending.
As such, every second, the ...
- 13
2
votes
1
answer
267
views
Is there a difference between instantaneous speed and the magnitude of instantaneous velocity?
Consider a particle that moves around the coordinate grid. After $t$ seconds, it has the position
$$
S(t)=(\cos t, \sin t) \quad 0 \leq t \leq \pi/2 \, .
$$
The particle traces a quarter arc of ...
- 131
0
votes
3
answers
145
views
What is the difference between two types of velocity?
What is the difference between $v=\frac{s}{\Delta t}$ and $\bar{v} =\frac{\Delta\bar{x}}{\Delta t}$, are they the same?
- 17
18
votes
8
answers
7k
views
Why do we need instantaneous speed?
I am new to this topic and was just wondering about the use of instantaneous speed. I mean, we use to calculate the speed of car let us say at 5 sec. So we take the distance travelled in 4.9 to 5.0 ...
- 735
1
vote
3
answers
2k
views
How does instantaneous speed work for circular motion?
Why do we use the formula $\lim_{\delta t→0} \delta s/\delta t$ to get the instantaneous speed? Since speed is distance divided by time, what does the limit have to do with this? I have a very limited ...
- 341
0
votes
4
answers
672
views
Question about $a = v\ \mathrm dv/\mathrm dx$
Consider $\vec{v}$ Now differentiating this w.r.t time,
$$\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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