Kinetic energy = (1/2) (mass) (speed)²
The rock's kinetic energy is not
(1/2) (4 kg) (10 m/s)²
= (1/2) (4 kg) (100 m²/s²)
= 200 Joules .
It may be more, or it may be less. The only thing
we can be sure of is that it is not 200 Joules.
12 newtons is your answer
Here in order to find out the distance between two planes after 3 hours can be calculated by the concept of relative velocity
here
speed of first plane is 700 mi/h at 31.3 degree
speed of second plane is 570 mi/h at 134 degree
now the relative velocity is given as
now the distance between them is given as
so the magnitude of the distance is given as
miles
so the distance between them is 2985.6 miles
I think it was either Robert Hook or Anton Van Leevwen Hoek