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for all your physics nerd out there...
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| stk |
This question has stumped me, it seems like an easy problem, im sure that i did all my calculatoins right and still the answer is wrong and i am baffled...anyways here is the question...
the question:
A hot air balloon is ascending at the rate of 14 m/s and is 79m above the ground when a package is dropped over the side. How long does it take the package to reach the ground?
the answer:
distance Y = 79m and initial velocitiy is 14 m/s and acceleration is 9.8 m/s^2. With these quanitites i solved for final velociity, which came out to be 41.77 m/s (this i am 100% correct on). Now to find the total time it takes to reach the ground, we know that final velocity is 41.77 m/s, initial 14 m/s and acceleration 9.8, so i simply solved for time using the fundamental equation of constant acceleration (final velocitiy = initial velocity + acceleration * time) and got 2.83...HOWEVER 2.83 is NOT the answer?? can anyone verify my work? thanks |
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| Resnick |
its cuz ur initial velocity is -14 (its going upward not downward)
this will not change the final velocity (when it hits the ground) but ur not accounting for the time it takes it to go up and come back down to its initial point (79m above ground)... |
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| ebeneezer_goode |
:eyes: i guess that's correct because i didnt understand it :P
i got 21 out of 70 in the physics test i had a week ago :( i suck at it, shouldnt have picked it at a-level :nervous: |
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| Inertia |
| just had my physics exam today... actually, its the other way around, your initial velocity is 14m/s, because it is upward. downward velocity is negative, therefore gravity is percieved as negative. so you must first calculate how long it takes for an object launched upward at 14m/s to start to descend due to the negative acceleration of gravity (-9.8m/s). this adds to your time, your distance and to your final velocity as well if im not mistaken. |
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| kypez |
| Very simple question. Wait till you take Quantum physics in unversity. You need to be on acid to understand whats going on.. |
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| physe |
| quote: | Originally posted by kypez
Very simple question. Wait till you take Quantum physics in unversity. You need to be on acid to understand whats going on.. |
You just need to keep reminding yourself: It's just math. |
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| stk |
| thx guys for all your help! |
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| cbxzcm |
| I'm curious to what the answer is. I got 5.69 seconds. |
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| starglider |
| quote: | Originally posted by Inertia
actually, its the other way around, your initial velocity is 14m/s, because it is upward. downward velocity is negative, therefore gravity is percieved as negative. so you must first calculate how long it takes for an object launched upward at 14m/s to start to descend due to the negative acceleration of gravity (-9.8m/s). this adds to your time, your distance and to your final velocity as well if im not mistaken. |
To be fair, downward velocity isn't negative. It is whatever we define it to be. Of course, upward velocity must then be opposite to it. |
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| EriK_V |
| quote: | Originally posted by cbxzcm
I'm curious to what the answer is. I got 5.69 seconds. |
well assume that up is positive and down is negative.
solve for time in the equation:
-1/2(9.8 m/s^2)t^2 + 14(m/s)t + 79m
t = 5.69s |
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| Unimog |
package has speed 14 m/s when dropped
now acc. is -9,81 m/sē
hmm after 1,42 sec. it has speed 0 m/s
in this 1,42 sec the package is ascending 9.89 meters
88.89 meter fall will take 4.25 sec
uhm i am sure this is wrong :D |
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| RenderedDream |
t(drop from ballon to v=0)= 1.42857s
y=89m
t(fall from 89m)=4.26s
v(when reaches superficie)=41.75m/s
these are my results, assuming that we can consider this vertical movement as an obliquous particle launch, i'm not sure if i can do this =P |
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