MHB How does tikx help to create graphs for a car's motion?

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The discussion focuses on using the TikZ package to create graphs representing a car's motion, including position, velocity, and acceleration. The car accelerates from rest to a speed of 2 m/s over 8 seconds, travels 60 meters at constant speed, and then decelerates to a stop at a red light, covering a total distance of 180 meters. Participants debate the appropriate axes for the graphs, suggesting that time should be on the x-axis and distance on the y-axis, while also clarifying the shapes of the graphs under constant acceleration and deceleration. There is confusion regarding the representation of speed and the nature of the graphs, with some participants correcting the initial speed assumption to 20 m/s. The conversation highlights the complexities of accurately depicting motion through graphical representation.
karush
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from tikx package...

\begin{tikzpicture}
%\draw (0,5) -- (6,5);
\draw [thick] (0,1) -- (18/2,1);
\node at (0,.8){0};
\node at (18/2,.8){180};
%\draw (1,5)--(1,4)--(2,4);
%\node at (1.5,4.1) {v};
\draw[step=.45 cm,gray,very thin,dashed]
%(-6,0)
grid (18/2,8);
\end{tikzpicture}

At $t=0$ a car is stopped at a traffic light
When the light turns green, the car starts to speed up,
and gains speed at a constant rate until it reaches a speed of $2 m/s \, 8s$ after the light turns green.
The car continues at a constant speed for $60m$
Then the driver sees a read light up ahead at the next intersection, and starts slowing down at a constant rate.
The car stops at the red light, $180 m$ form where it was at $t=0$a) Draw $x_t, v_t,$ and $a_t$ graphs for the motion of the car
b) In a motion diagram show the position, velocity and acceleration of the car.ok I am tying to do this using tikx but got stuck at the beginingI currently have the x-axis at distance but maybe it shud be time
we might need actually 2 graphs

I think the velocity is really $2m/s$
$v = v_0 + at$
then
$\dfrac{v-v_0}{t}=a$
so
$\dfrac{2m/s}{s}=\dfrac{2m}{s^2}=a$
 
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If you have the x-axis as distance, what is the y-axis? I suggest that the x-axis be t, time, and the x-axis be the distance traveled in that time. At constant speed the graph is a straight line, at constant acceleration or deceleration the graph is a parabola.
 
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why would a constant acceleration be a parabola the slope doesn't change

I think one graph a-t would be the one I should do

here is sample from another problem from google images

View attachment 9249
 

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The speed of $2\text{ m/s}$ seems rather low for a car — it's a walking speed.

Either way, we could for instance draw the graphs like this:
\begin{tikzpicture}[xscale=0.2,yscale=.04]
%preamble \usepackage{amsmath}
\draw[xstep=2,ystep=10,lightgray,very thin] (0,-20) grid (150,260);
\draw (8,0) -- (8,250) (38,-18) -- (38,100) (150,-18) -- (150,180);
\draw[thick,->] (0,0) node[below] {0 s} -- (8,0) node[below] {8 s} -- (38,0) node[below] {38 s} -- (150,0) node[below] {150 s} -- (155,0) node
{$t$};
\draw[thick,->] (0,0) -- (0,260);
\draw[ultra thick,red] (0,250) -- node[below] {$a_t$} (8,250) node
{$0.25\text{ m/s}^2$} -- (8,0) -- (38,0) -- (38,-18) node
{$-0.018\text{ m/s}^2$} -- (150,-18);
\draw[ultra thick,cyan] (0,0) -- node[above left] {$v_t$} (8,100) node
{2 m/s} -- (38,100) node[above] {2 m/s} -- (150,0);
\draw[ultra thick,blue] (0,0) parabola (8,8) node[above left] {8 m} -- node[above left] {$x_t$} (38,68) node[below right] {68 m} parabola bend (150,180) (150,180) node[above] {180 m};
\end{tikzpicture}​
 
yeah I think it should be 20 not 2
the copy was really hard to read...
that would make the horizontal lite blue line to 8+3=11s
wow thanks for the graph

ok I did this fot a-t and 20 m/s

\begin{tikzpicture}[xscale=0.2,yscale=.04]
%preamble \usepackage{amsmath}
\draw[xstep=2,ystep=10,lightgray,very thin] (0,0) grid (40,160);
%\draw (8,0) -- (8,250) (38,-18) -- (38,100) (150,-18) -- (150,180);
\draw[thick,->]
(0,0) node[below] {0 s}
-- (16,0) node[below] {8 s} -- (11*2,0) node[below] {11 s} -- (15*2,0) node[below] {15 s} -- (40,0) node
{$t$};
\draw[thick,->] (0,0)-- (0,100) node
{20 m/s} -- (0,160);
%\draw[ultra thick,red] (0,250) -- node[below] {$a_t$} (8,250) node
{$0.25\text{ m/s}^2$} -- (8,0) -- (38,0) -- (38,-18) node
{$-0.018\text{ m/s}^2$} -- (150,-18);
\draw[ultra thick,cyan] (0,0) -- node[above left] {$v_t$} (8*2,100) -- (11*2,100) -- (30,0);

% \draw[ultra thick,blue] (0,0) parabola (8,8) node[above left] {8 m} -- node[above left] {$x_t$} (38,68) node[below right] {68 m} parabola bend (150,180) (150,180) node[above] {180 m};
\end{tikzpicture}

clueless about the speed parabola​
 
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