Because the number of valence electrons of an element determines the properties and in particular the reactivity of that element.
In fact, elements of the first group (i.e. only one valence electron) have high reactivity, because they can easily give away their valence electron to atoms of other elements forming bonds. On the contrary, elements of the 8th group (noble gases) have their outermost shell completely filled with electrons, so they do not have valence electrons, and they have little or no reactivity at all.
Answer:
C. a disturbance that travels through a medium with a transfer of energy and without a transfer of matter
Explanation:
A wave is any disturbance that transfers energy from one location to the other via a substance called medium. It is important to note that a wave only conveys energy and not matter. For example, sound wave is a type of wave that carries sound energy from one place to another via mediums such as water, air etc.
Hence, according to this question, a wave can be described as a disturbance that travels through a medium with a transfer of energy and WITHOUT A TRANSFER OF MATTER.
The study of sound is called sonics and the study of sound waves are acoustics
A bird in the hand is worth two in the bush
or
actions speak louder than words
or
her bark is worse than her bite
i hope this helps these are examples of aphorism
Answer:
49 N
Explanation:
In order to move the box at constant speed, the acceleration of the box must be zero (a=0): this means, according to Newton's second law,
F = ma
that the net force acting on the box, F, must be zero as well.
Here there are two forces acting on the box in the horizontal direction while it is moving:
- The force of push applied by the guy, F
- The frictional force, 
For an object moving on a flat surface, the frictional force is given by
where
is the coefficient of friction
m is the mass of the box
g is the acceleration of gravity
So the equation of the forces becomes
And substituting:
We find the force that must be applied by the guy:
