How much force would it take to throw a 400g American football over the house drawn?

2017-04-16 9:29 pm

回答 (2)

2017-04-16 11:13 pm
✔ 最佳答案
Oh wait...that's clearly Australian football as the house is on the bottom half of Earth and hanging upside down.

So we have the following constraints: it must travel X = SUM(x) = 6.1 + 7.4 + 12.4 meters in range, reach max height H at X/2, and H must be greater than 7.4 m.

As the ball is assumed caught at the same height it's tossed, the flight time T = Tu + Td = 2sqrt(2H/g) = 2*sqrt(2*7.4/9.8) = ? seconds. Then X = Ux T; so that Ux = X/T is the horizontal component of the toss.

To reach H, we must have H = Uy^2/2g where Uy is the vertical component and U^2 = Ux^2 + Uy^2 gives us the toss speed to clear the house and make that range X. So U = sqrt((X/T)^2 + 2gH) = sqrt(((6.1 + 7.4 + 12.4)/2*sqrt(2*7.4/9.8)) + 2*9.8*7.4) = 12.7 m/s is the required toss speed.

But here's the rub. As U = At = (F/M)t so that F = MU/t we need to know t, the time spent in actually throwing the ball at the speed U. As you can see, it'll take more force F to toss anything at U speed when the time spent throwing is short versus longer. BTW in case you don't see it F = MU/t is a variation of impulse.
2017-04-16 9:37 pm
How long far does the ball travel while that force is applied?


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