Laura can jump a vertical distance of 0.85 m. what is the total time she is off the ground? with what velocity does she hit the ground?

0.42 s, -4.1 m/s

Explanation:

The time it takes to reach 0.85 meters is the same as the time it takes to fall back to the ground.

y = y₀ + vt − ½ at²

0.85 m = 0 m + (0 m/s) t − ½ (-9.8 m/s²) t²

t = 0.42 s

It takes 0.42 seconds to reach the maximum height.  So it takes another 0.42 seconds to land.  Therefore, Laura is in the air for 0.84 seconds.

v² = v₀² + 2a (y − y₀)

v² = (0 m/s)² + 2(-9.8 m/s²) (0 m − 0.85 m)

v = -4.1 m/s

Laura hits the ground at a velocity of -4.1 m/s.

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