Answer:
u = 9.2 m/s
Explanation:
Second equation of motion:
s = u t + 0.5 a t²
The time in which book would fall 35.4 m downwards is:
Initial velocity is zero in vertical direction.
35.4 = 0 + 0.5 (9.8)t²
⇒ t² = 7.22 ⇒t = 2.68 s
The horizontal distance covered by Henrietta in (7.00 s+ 2.68 s):
x = 2.55 m/s × 9.68 s = 24.684 m
The initial velocity with which the book must be thrown in order for Henrietta to catch.
24.684 m = u ( 2.68 s)
u = 9.2 m/s