5th Grade science project about hydropower

[deleted-404640]

Hello. My son has made a compound machine with turbine, wheel, and axle to lift varying weights of metal objects. For the current phase of his project, the flow is kept constant ( meaning we haven't manipulated the faucet flow since calculating the flow rate) . My son did find that it took longer to wind up the heavier objects on the string at a constant flow, however, the amount of time needed has not increased linearly. The weights of his objects are 4 gms, 7 gms, and 17 gms. The time difference is only about 1.5 seconds to wind up the smallest and heaviest object. He is wondering how the heaviest object didn't require quite a bit more time? This is where I need help. Can you offer some info as to why the work needed to lift the varying weights changes as expected, but not by the amount that my son would expect? The second phase of his project he will alter the flow rate and watch what happens to the work required to lift only one object. His project title is either going to be Water's Potential or Go With the Flow.

Thank you

[MadelineB]

Hello ssw2016,
This is an awesome project for a student in grades K-5! I'm sorry to see that none of the experts here at Science Buddies have replied to your post. I will add a reminder in the Experts Forum to see if someone can respond.

Thank you for your patience.

[deleted-404640]

Thank you very much for your response. My son has been checking daily to see if someone has responded. We have continued to think of our problem. The only explanation that we can come up with on our own is the flow rate may fluctuate coming into our house. Maybe it's changing slightly even without us manipulating the faucet.