does weight affect bounce of an object off a trampoline?

[samanthalevy]

I am working on a project about if weight affects the bounce off a trampoline. I know weight doesn't affect the rate at which the object will fall(gravity) but will the weight affect the elastic potential energy? I will use varing size/weight balls (compare bowling ball/soccer ball;compare pingpong ball/golf ball etc) and drop them from the same height onto the trampoline and try to observe if the bounce varies. How do I measure the height of the bounce? Do i focus on ths springs(hooke's law) using a ruler on the springs(7"extension springs)? or rather focus on the objects rebounding off the trampoline by rigging a tape measure and taking digital picures?Can i use myself instead with /without added weights? or will i become an added unwanted varible,as my bounce technique will be inconsistant. i found a website to calculate force exerted onto the springs-is this the right track?I'm really not sure how to do the measuring and keep it on track scientifically.Is it possible? Will the balls be enough weight to effectively get accurate results or should i focus on using something heavier than balls?..bricks and styrofoam? will the round objects affect the outcome? thanks for any suggestions.

[MelissaB]

Samantha,

Personally, if I were doing this experiment I would set up a digital video camera to record the resulting bounces. Also, it may help to have some sort of a scale on the wall behind the trampoline so you can measure how high the bounces were. I would just think it would be very difficult to both drop something and then estimate how high it bounced accurately without two people.

I would focus on the bounces themselves because I suspect that there will be more variation in them than in the amoun the springs stretch--so it will be easier to measure and compare.

I think it would be neat to include, along with the balls, you jumping on the trampoline with and without weights. As you've said, your bounce technique may vary, but since you're aware of that you can do your best not to vary it--and with a digital video camera you should be able to see if you're doing anything drastically different.

If you weren't already planning on it, I suggest doing multiple trials with each ball so you can get an average bounce height.

I think balls will be okay and that you won't need to resort to bricks/styrofoam--but if you're worried, do some tests on your own with the balls you plan to use and see if the bounces are high enough to get useful readings.

Hope this helps!

[Louise]

Samantha,

Personally, if I were doing this experiment I would set up a digital video camera to record the resulting bounces. Also, it may help to have some sort of a scale on the wall behind the trampoline so you can measure how high the bounces were. I would just think it would be very difficult to both drop something and then estimate how high it bounced accurately without two people.

I would focus on the bounces themselves because I suspect that there will be more variation in them than in the amoun the springs stretch--so it will be easier to measure and compare.

I think it would be neat to include, along with the balls, you jumping on the trampoline with and without weights. As you've said, your bounce technique may vary, but since you're aware of that you can do your best not to vary it--and with a digital video camera you should be able to see if you're doing anything drastically different.

If you weren't already planning on it, I suggest doing multiple trials with each ball so you can get an average bounce height.

I think balls will be okay and that you won't need to resort to bricks/styrofoam--but if you're worried, do some tests on your own with the balls you plan to use and see if the bounces are high enough to get useful readings.

Hope this helps!

I think it might be interesting to do it both ways- measure the springs and the video of the bounce. They should give you similar results. If they don't, that is an intriguing question- where is that energy going. Plus, if one method turns out to be not so good, you already have a backup set of data!

I think the scale Melissa suggests is a really good idea, as are mutiple trials. I'm guessing the lighter objects won't work well- they probably won't deform the trampoline much at all and not have a significant different in height. (They will probably bounce, but due to the tension in the fabric, not the springs of the trampoline, I would guess. Doesn't mean you shouldn't do it, since I could be wrong!)


Louise

[deleted-71588]

My engineering intuition thinks you maybe missing a control. In engineering terms, you are proposing a compound physics problem. See if you can figure out why it is compound after reading what follows.

Break it down. If you drop an inflated ball (ping pong balls count as being gas filled) onto a flat hard surface, what do you expect it to do? My expectation they will bounce. Maybe you want to try dropping each different ball (excluding hard core ones like the bowling ball and crochet ball you don't want to damage) in your experiment from the same height you plan to use with the trampoline onto a hard surface and measure the bounce height as a control series.

Think about something like a balloon that is more compressible. What happens when it hits or is pushed into a hard surface? I expect it to deform and when you let go of it, Sr. Isaac Newton and others predicts it is going to move as it equilizes the internal surface pressures.

Think about how you "kill" your bounce to stop quickly and think about how this might apply to something compressible.

I have no clue what you are going to see in your results because I don't know enough specifics and it would be hard to even try to measure them, so I expect you to see some interesting results. Compound physics experiments are interesting if you like challenges.

[samanthalevy]

Thanks craig the control series sounds like a good idea. I'm in 5th grade so you confused me some. so far i made a plastic sphere and attached a tape measure so i could control the drop height and rebound bounce to measure more accurately.melissa and louise:thanks!I used a video to rewind and check actual bounce height. I've done days of research and learned alot about my topic.i am having a hard time explaining my results i think part of the reason is i learned alot of things factor into bounce height and by using a trampoline in the equation i added more factors in. i did 10 bounces for each ball ( the results for each of the 10 bounces were pretty close to each other-but i did average them for my graph i included each bounce as reference as to how i got my average) my results:
ping pong weight .1o oz bounce 20.3 inches
air ball .50 oz 19.5inches
bouncy ball .70oz 20.3 inches
golf ball 1 lb .60oz 19.5inches
tennis ball 2lb .30oz 16.9 inches
baseball 5lb 13.7inches
questions I still have... HELPPPPPPPPPPPPP
my research paper explains why balls bounce...energy changes, never lost....ball design affects bounce....surface affects bounce...drop height(which remained constant innmy experiment) affects bounce...gravity....how trampolines are made...what affects bounce of trampoline(weight ,springs, nylon, force of jumper ,force causing bounce to stop)...elasticity...springs



Can i leave out other reasons that might affect bounce and only explain my results based on weight which is what my project is about(knowing thi is not the only thing)?(when i write my conclusion for my board)
I know the ping pong and bouncy ball are similar in size/weight and bounce is same. All balls were close in bounce except tennis and baseball. Tennis balls are designed to bounce not baseballs so weight was an issue in lower bounce of tennis ball ..right?

I am also unable to find any other experiments like tis and our teacher wants us to include this in our resaerch paper. Do i just refer to other "bounce experiments" not experiments by kids but real scientists ..i think made that prove the thoeries we are using? thanks for any help