Answer:
4.1 N
Step-by-step explanation:
We can solve this problem by using considerations about energy.
At the moment the stone is dropped, it has only gravitational potential energy:

where
is the weight of the stone
h = 10 m is the initial height of the stone
As the stone falls, part of this energy is converted into kinetic energy, while part into thermal energy due to the presence of the air friction, acting opposite to the motion of the stone:

where:
is the mass
v = 13 m/s is the final speed of the stone
is the thermal energy
The thermal energy is actually equal to the work done by the air friction on the stone:

where
F is the average force of friction
h = 10 m
Since the total energy must be conserved, we can combine the three equations, so we find:

And solving for F, we find the average force of air friction:

Answer:
A is the true answer and others are wrong
Answer:
2) Add 21 to both sides
Step-by-step explanation:
When solving
for
, our goal to isolate
such that we have
set equal to something.
Therefore, we want to start by adding 21 to both sides. This leaves us with
and we are one step closer to isolating
.
The new figure is formed differently and is not the same as the other ome