Question

27. Using energy considerations and assuming negligible air resistance,
show that a rock thrown from a bridge 20.0 m above water with an initial
speed of 15.0 m/s strikes the water with a speed of 24.8 m/s independent
of the direction thrown.

Answer 1

(1/2) m Vi^2 + m g h = (1/2) m Vfinal^2
or
Vfinal^2 = Vi^2 + 2 g h

= 225 + 2 (9.81)(20)

= 617.4

sqrt 617.4 = 24.8

Answer 2

24.8

Answer 3

I have a fought in the question value of m is not given .
Then how you have found the kinetic energy???