- Downward motion
So, the stone goes up for 2 sec. The distance covered in these 2 sec can be found by
2gs = vf2 – vi2. Put the values,
2(-9.8)s = 0 – (19.6)2 Or s = (19.6 * 19.6)/(2 * 9.8) Or s = 384.16/19.6 = 19.6 m
So, the total distance the stone drops through is (156.8 + 19.6) = 176.4 m under the action of gravity. Therefore, to find time t, we apply, s = vit + ½ at2, where vi = 0. Put the values,
176.4 = 0 + ½ × 9.8 × t2 Or 176.4 = 4.9t2 Or t2 = (176.4)/4.9 = t2 = 36 Or t = 6 s … (2)
What if we solve this problem simply by putting values in the equation “time= distance / speed”?
Sana
Formula t = s/v is applicable only in the case when a body is moving with uniform velocity. Here the stone is continuously under the influence of gravity and the velocity is changing every moment.
Nice
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