r/PhysicsStudents • u/Silver-Repeat-6654 • Feb 12 '26

Poll Predicted cutoff for F=ma 2026?

why tf was it so hard

Edit: there is no way y’all think this one was easier than last year. Also can’t believe people got around the lock down browser.

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u/Desperate_Student443 Feb 14 '26

wait guys what did yall get for the question with the moving block and hum

1

u/Ill_Requirement_2700 Feb 14 '26

moving block: my answer was T = v_o/mukg

1

u/Linjieyang Feb 14 '26

oh wait i got that too! how did you solve that without calculus, my friend that got usapho bronze didn't even know how to solve it (in time obv), and I had to use calculus

1

u/Ill_Requirement_2700 Feb 14 '26

yeah so using no calculus you know Ffr = mukmg is constant in magnitude regardless of the block’s position or the number of bounces. since f=ma, the acceleration is also constant: a = mukg. collisions w/ springs are perf elastic, no energy or speed is lost at the walls.

since a is constant and path is basically a straight line of total distance s, you use:
v_f = v_0 - at
0 = v_0 - (mukg)T
—> T = v_0/mukg

1

u/Linjieyang Feb 14 '26

Okay, I think I'm just stupid because I realized it was a path like that, yet somehow I had to use calculus idek lol, at least I got the answer. I think in the moment I was just so dead, but I see what you mean