Answer: 185.5672566
Explanation: The friction is not relevant
Normal reaction is the force perpendicular to the surface.
this force resists the downwards forces applied which are gravity and a component of the applied force.
Wee can use here kinematics
as we know that

for shorter tree we know that


now since we know that other tree is twice high
So height of other tree is y = 39.2 m
now again by above equation



so the time taken is 2.83 s
1) 29.4 N
The force of gravity between two objects is given by:

where
G is the gravitational constant
M and m are the masses of the two objects
r is the separation between the centres of mass of the two objects
In this problem, we have
(mass of the Earth)
(mass of the box)
(Earth's radius, which is also the distance between the centres of mass of the two objects, since the box is located at Earth's surface)
Substituting into the equation, we find F:

2) 
Let's now calculate the ratio F/m. We have:
F = 29.4 N
m = 3.0 kg
Subsituting, we find

This is called acceleration of gravity, and it is the acceleration at which every object falls near the Earth's surface. It is indicated with the symbol
.
We can prove that this is the acceleration of the object: in fact, according to Newton's second law,

where a is the acceleration of the object. Re-arranging,

which is exactly equal to the quantity we have calculated above.
Answer: The option (C) is correct. The energy travels horizontally.
Explanation: When the pebble is thrown into a calm lake, there will be disturbance in the lake. The ripples are formed from the center and move outward because the energy is carried out from particle to particle.
The distribution of the energy among the particles starts from center and it will carry out outward. This disturbance will occur horizontally.
Therefore, the energy travels horizontally.