Question #125387

• A 50.0 kg circus acrobat drops from a height of 2.0 m straight down onto a springboard with a force constant of 8.00 × 103 N/m. By what maximum distance does she compress the spring?

• Using energy considerations and assuming negligible air resistance, show that a rock thrown from a bridge 20.0 m above water with an initial speed of 15.0 m/s strikes the water with a speed of 24.8 m/s independent of the direction thrown.

Expert's answer

1.As "U_g=mgh,PE=\\frac{1}{2}kx^2" then from "U_g=PE" hence "x=\\sqrt\\frac{2mgh}{k}=\\sqrt\\frac{2\\sdot50\\sdot9.8\\sdot2}{8\\sdot10^3}\\approx0.5m"

2.As "mu^2\/2=mgh+mv^2\/2" hence "u=\\sqrt{2gh+v^2}=\\sqrt{2\\sdot9.8\\sdot20+15^2}\\approx24.8m\/c"

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