A ball is thrown up in the air. Its height h, in meters after a time of t seconds is given by h= -4.9t2+38t+1.75. How long is the ball above 50 meters? Round to two decimal places.

Question

It would mean alot if someone could help me!!

Answer 1

We need to know t when h>50, so -4.9t²+38t+1.75>50.

This can be written: 4.9t²-38t+48.25<0

Using the quadratic formula: t=(38±√(38²-4×4.9×48.25))/9.8=6.15537 and 1.59973 seconds. The ball is above 50m between these times, so that’s 6.15537-1.59973=4.56 seconds to 2 decimal places.