A student throws a set of keys vertically upward to her sororitysister, who is i

Question

A student throws a set of keys vertically upward to her sororitysister, who is in a window 4.10 m above.The keys are caught 1.30 s later by thesister's outstretched hand.(a) With what initial velocity were thekeys thrown?

(a) With what initial velocity were the keys thrown?

(b) What was the velocity of the keys just before they werecaught?

Could someone explain how to do this problem step by step becauseas I plug in my values to my equations with t=0 for the initialvelocity it tells me that my answer is off by 10%? Can someoneplease help me? You help will be much appreciated.

Explanation / Answer

   height, h = 4.1 m    time, t = 1.3 s    initial velocity, u = ?    final velocity, v = ? (a)   s = ut + (1/2) at2        h = u (1.3) - (1/2)gt2       4.1 = u (1.3) - 4.9 ( 1.3)2      by solving, u = 9.52 m/s (b)   v = u + at = u - gt = 9.52 - ( 9.8) (1.3) = -3.22 m/s ( here '-' indicate downward direction)      by solving, u = 9.52 m/s (b)   v = u + at = u - gt = 9.52 - ( 9.8) (1.3) = -3.22 m/s ( here '-' indicate downward direction)

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