Answer:
5 W
Explanation:
The formula of the power is:
● P = W/t
W is the work and t is the time needed to do it(in seconds)
Let's calculate first the work that the force exerced:
W = Vector F . Vector d
D is the distance ( here 400 cm wich is 4 m)
Make a representation to see how are the vectors F and V.(picture below)
The vector F and d are colinear since Den is pushing the desk on the ground.
● W = 4 × 10 = 40 J
J is Joule
■■■■■■■■■■■■■■■■■■■■■■■■■■
● P = W / t
● P = 40/ 8
● P = 5 W
To solve this problem we will apply the principles of conservation of energy, for which we have to preserve the initial kinetic energy as elastic potential energy at the end of the movement. If said equality is maintained then we can affirm that,
Here,
m = mass
k = Spring constant
x = Displacement
v = Velocity
Rearranging to find the velocity,
Our values are,
Replacing our values we have,
Therefore the velocity is 
I'm sure you've noticed that an airplane high in the sky, far away
from you, looks like it's moving very slowly. At the same time,
somebody passing you on a skateboard whizzes past you at
high speed. The farther away something is from you, the slower
it appears to move.
The nearest star outside the solar system is almost 32 thousand times
as far away from us as the farthest visible planet (Saturn) is, and all of the
other stars are farther than that.
That's why you have to wait a few thousand years before you notice
that the shape of a constellation has changed.
To put it a slightly different way . . . Everything is in motion. The motion is
more noticeable for nearby things, and less noticeable for farther-away things.
Objects within our solar system are the only ones near enough so that a human
lifetime is a long enough period in which to notice the change in their position.
Even Pluto moves less then 1.5° against the 'background' stars in a whole year.
This all makes me feel small. How about you ?
