What force controls the movement of the planets around the sun, holds together stars grouped in galaxies, and galaxies grouped i
1 answer:
Answer:
Gravity.
Explanation:
The force that controls the movement of the planets around the sun, holds together stars grouped in galaxies, and galaxies grouped in clusters is called gravity.
This ultimately implies that, gravity is considered to be a universal force of attraction that acts between all objects that has both mass, energy and occupy space. Therefore, it acts in such a way as to bring objects together.
Additionally, the gravity of earth makes it possible for all physical objects to possess weight.
Weight can be defined as the force acting on a body or an object as a result of gravity.
Mathematically, weight is given by the formula;
Where;
m is the mass of an object.
g is acceleration due to gravity.
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1) Focal length
We can find the focal length of the mirror by using the mirror equation:
(1)
where
f is the focal length
is the distance of the object from the mirror
is the distance of the image from the mirror
In this case,
, while 
(the distance of the image should be taken as negative, because the image is to the right (behind) of the mirror, so it is virtual). If we use these data inside (1), we find the focal length of the mirror:
from which we find
2) The mirror is convex: in fact, for the sign convention, a concave mirror has positive focal length while a convex mirror has negative focal length. In this case, the focal length is negative, so the mirror is convex.
3) The image is virtual, because it is behind the mirror and in fact we have taken its distance from the mirror as negative.
4) The radius of curvature of a mirror is twice its focal length, so for the mirror in our problem the radius of curvature is:
We can find the focal length of the mirror by using the mirror equation:
where
f is the focal length
In this case,
from which we find
2) The mirror is convex: in fact, for the sign convention, a concave mirror has positive focal length while a convex mirror has negative focal length. In this case, the focal length is negative, so the mirror is convex.
3) The image is virtual, because it is behind the mirror and in fact we have taken its distance from the mirror as negative.
4) The radius of curvature of a mirror is twice its focal length, so for the mirror in our problem the radius of curvature is:
Explanation:
It is given that,
Mass of the football player, m = 92 kg
Velocity of player, v = 5 m/s
Time taken, t = 10 s
(1) We need to find the original kinetic energy of the player. It is given by :
k = 1150 J
In two significant figure,
(2) We know that work done is equal to the change in kinetic energy. Work done per unit time is called power of the player. We need to find the average power required to stop him. So, his final velocity v = 0
i.e.
P = 115 watts
In two significant figures,
Hence, this is the required solution.