Question

A particle is projected vertically upwards from ground level with a speed of 50 m/s. For how long willit
more than 70 m above the ground ? (g = 10 m/s2)
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Answer 1

Answer:

1.75 seconds

Explanation:

This is a quadratic equation. Plugging in the given values, $y=-10x^{2}+50x$ when y is the height of the object after x seconds. Use 70 as the y-value, then solve for x:

$70=-10x^{2}+50x$

x = 1.75