15
votes
Can $d/t =$ speed ever be wrong? Is there a more accurate way to determine speed?
I'm very sorry for your loss.
The definition of the average speed of an object as it passes between two points is the distance $d$ between them divided by the time $t$ it took to get from one to the ...
- 63.4k
8
votes
What happens physically when object is thrown up when $v$ becomes 0 at max height?
This is the kind of question that is better answered with an appeal to mathematical unity.
Draw the velocity time graph. You should get a straight line graph from positive velocity at initial time, ...
- 5,023
4
votes
Accepted
Velocity at impact
Yes. You can either argue from the need for the velocity or momentum to be a continuous function of time, or the fact that the ground will, at some time, have imparted enough momentum upwards on the ...
- 5,023
2
votes
What happens physically when object is thrown up when $v$ becomes 0 at max height?
Good answers are provided, I only want to address your statement that:
i want to understand what actually happens in this scenario
To do that, you would have to conduct an experiment. While we model ...
- 1,247
2
votes
Is the way of determining my angle of vector wrong or am I using the wrong formula for calculating magnitude of resultant?
Your approach is way off, and you really don't need to use vectors for this.
First find the distance traveled by the first ball:
$$d_A(t) = a_At^2+v_At$$
then find the distance traveled by the second ...
- 6,442
2
votes
Velocity at impact
Typically a ball is idealized as a point particle or rigid object. A collision is idealized as instantaneous. The idealizations work for problems where you ask about velocity before and after. But ...
- 33.3k
1
vote
Velocity at impact
In real life, yes it does! If this wouldn't have been the case, then the ground is supposed to provide an infinite amount of force to the ball which is not possible in real life scenarios. Moreover ...
- 549
1
vote
Velocity at impact
Does the momentary velocity become zero ?
Yes, as long as you assume a physically realistic scenario in which the ball and/or the ground deforms (even if only slightly). In this case the velocity of ...
- 42.1k
1
vote
Why vectors change under boost along some axis?
Note that the greek subscript on the vector implies (by convention) that it is a 4-vector, which has a variety of representations (lexically, not group theory):
$$ a_{\mu} = (a_0, a_1, a_2, a_3) $$
$$ ...
- 29.2k
1
vote
Accepted
Is the way of determining my angle of vector wrong or am I using the wrong formula for calculating magnitude of resultant?
The relative velocity is the difference between the two velocity vectors. This is alwayas so, by definition if you want. It does not matter which way are the directions of the two vectors.
So, if you ...
- 7,811
1
vote
Can $d/t =$ speed ever be wrong? Is there a more accurate way to determine speed?
$d/t$ is the average speed. Consider a simple case: if someone needs to brake for $t=2 \, s$ to finally immobilize the car and during that time he/her travels a distance $d=22 \, m$, $d/t$ would ...
- 63
1
vote
Can $d/t =$ speed ever be wrong? Is there a more accurate way to determine speed?
In this case, it would not be about the fundamental calculation such as d/t, but the tell tale clues and their incorporation into the calculation. Fuzzy data, so to speak. There is difficulty of ...
- 8,430
1
vote
Spatial coordinates in Eulerian specification of velocity field
To help understand what is happening, an exemple can be useful. Consider the time-independent (Eulerian) velocity field : $$\vec{u(M)}=ax \vec{e_x}$$
We are looking for the trajectory $X(x_0,t)$ of ...
- 4,321
1
vote
Direct conversion of cartesian velocity to spherical velocity and vice-versa
Notice that $\frac{d\theta}{dt}$ and $\frac{d\phi}{dt}$ do not have units of velocity (m/s), so right there you have a problem.
Velocity in the $\hat \theta$ direction is "how much distance $ds$ ...
- 6,442
1
vote
Accepted
Direct conversion of cartesian velocity to spherical velocity and vice-versa
This is one of those things that will, upon closer inspection, turn out to be horrible and confusing. Let us compute some stuff, with suggestive notation chosen to make the understanding easier.
...
- 5,023
1
vote
What happens physically when object is thrown up when $v$ becomes 0 at max height?
Velocity is displacement over time. If we take a point $P_a$ a little bit after the maximum height, it is always possible to find another one $P_b$ a little bit before it, so that both $P_a$ and $P_b$ ...
- 14.1k
1
vote
What happens physically when object is thrown up when $v$ becomes 0 at max height?
$v=\frac{dx}{dt}:= \lim\limits_{\Delta t \to 0} \frac{x(t+\Delta t)-x(t)}{\Delta t}$
Reading the expression in words:
"Velocity equals the rate of change of position with respect to time, which ...
- 12k
1
vote
Accepted
Velocity and acceleration of a ball shot uphill
Since the ball is rolling upward freely, there is no force along its upward path so drawing a simple force diagram we find that:
$$-mg\sin{\alpha} = ma \rightarrow -g\sin\alpha = a$$
Where we assume ...
- 1,247
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