Answer:
Efficiency is the percent of work put into a machine by the user (input work) that becomes work done by the machine (output work).
Explanation:
It is a measure of how well a machine reduces friction.
Answer: Before the jump, the snowboarder would carry potential energy.
During the jump he will carry kinetic energy.
And after the jump, assuming hes at a full stop, he will carry potential energy once again.
Answer:
Wave X has a shorter wavelength.
Explanation:
The relation between the speed of a wave, its wavelength and frequency is given by :

It can be seen that the relationship between the frequency and wavelength is inverse.
In this problem, it is mentioned that two sound waves (wave X and wave Y) are moving through a medium at the same speed. The frequency of wave X is greater than wave Y. Then it would mean that wave X have shorter wavelength than wave Y (due to inverse relation).
Answer: A- It would increase
Explanation:
According to the law of universal gravitation:
Where:
is the module of the attraction force exerted between both objects
is the universal gravitation constant.
and
are the masses of both objects
is the distance between both objects
As we can see, the gravity force is directly proportional to the mass of the bodies or objects and inversely proportional to the square of the distance that separates them.
In other words:
<h2>If we decrease the distance between both objects, the gravitational force between them will increase. </h2>
i’m pretty sure it’s , the alkali metals