Question

A ball is thrown upwards from the ground. It is
at a height 100 m in the upward and
the downward journey at times ti and t2
respectively. If g=10m/s2 then tı tz =​

Answer 1

Answer:

Let us take the point from which the ball is thrown up as the origin of coordinate system, the up direction as positive and down direction as negative. Let velocity of projection be u. Then the displacement s of the ball at any time t is given by

s = u t + ½ a t², where a = acceleration due to gravity = -10 m/s², s= +100 m

Substituting various values; 100 = u t - 5 t²; ========> 5 t² - u t + 100=0.

This is a quadratic equation. Let the two times when the ball is at 100 m height be t' and t'', the roots of the quadratic equation.

Then the products of the roots of a quadratic equation = constant term / coefficient of t² = 100/5 = 20.

So t' × t'' = 20 s²nation:

Explanation:

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