The Official AP Physics B Thread

<ol>
<li>The infamous spring problem. The first part is 1/2kx^2=mgh then solve for h.</li>
</ol>

<p>h=kx^2/mg</p>

<p>you can plot height versus x^2/mg, and the slope of that line is the constant</p>

<p>pigs- you’re missing a 1/2 in there</p>

<p>i did 1/m vs. 2gh/x^2.</p>

<p>woops typo</p>

<p>then for the last part</p>

<p>could you just have rearragned the equation
like kx^2/2=hmg, and plotted kx^2/2 versus mg, for which the slope yields the height??</p>

<p>ummm… you can’t plot kx^2/2 vs. mg because you’re looking for k. lol</p>

<p>no no for part d!! where it asked how to find teh maximum height</p>

<p>I plotted the force (N) by the distance (m) and those are the units for a spring constant so unless i screwed up bad that should be how you do it.</p>

<p>i think there are many ways to find the spring constant
that was a very open question…</p>

<p>i think it has to do with force=kx but idk thats but i tried to do but i failed lol</p>

<p>Oh yeah, you’re right lol</p>

<p>i said you could still do it experimentally (we actually did this lab in class, and you can tell when it’s at the max height)</p>

<p>you can’t plot force against distance because</p>

<p>a. distance is constant
b. since distance is constant and k is constant, force is constant. (so you’d get one plotted point)</p>

<p>Distance as in how far you stretch the spring, not the height it goes.</p>

<p>yeah, that’s constant</p>

<p>edit: nvm
i was lost in this convo</p>

<p>oh gosh lol
i’m printing out teh frq and i’m gonna go review it with the physics teacher at school tomorrow!!! yay</p>

<p>How to find the maximum height?
OMG i interpreted the question wrong…</p>

<p>I said to use many trials and estimate the height…
omg it meant algebratically!?!</p>

<p>DANG should i print it out?? i don’t wanna waste ink =[
should i just make my physics teacher pull it up from his computer on ap central??? lol</p>

<h1>1 was:</h1>

<p>1/2kx^2=mgh. solve for h.
then graph h and 1/m… solve for k with any plot points, k~490</p>

<p>But wouldn’t the h in mgh really be h (as drawn on the figure) + L0 - x? h in the figure is distance from the top of the compressed spring until to the spring in the air, not from the ground to the spring in the air.</p>

<p>Oh yeah, the first FR got me, so I basically BS on it. I said the two variables you need to determine k is F (which is mg) and x (which is 0.2). Then I plugged them on the chart and graphed it. Then I said k is infinity N/m.</p>

<p>I think they’ll give me full credit because it’s based on a previous mistake, right?</p>