It takes the moon about 27 days to revolve on its axis.
Answer:

Explanation:
F = Force = 
m = Mass of proton = 
t = Time taken = 
Acceleration is given by


The velocity of the proton is 
In science, a broad idea that has been repeatedly verified so as to give scientists great confidence that it represents reality is called "a theory".
<u>Explanation:</u>
In science, the interpretation of a feature of the organic world that can be tested in repeat manner and analysed by applying agreed tests validation methods, calculation and observation in according to the scientific method, such process is called as a theory in science.
The difference lie between a theory and a hypothesis. Because hypothesis is an "educated guess". Overall it is either a proposed interpretation of an observed phenomenon, or a logical inference of a possible causal association between several phenomena.
Answer:

Explanation:
The weight of an object on Earth is given by
, so we can calculate its mass by doing
, which for our values is:

<em>Nothing is being asked</em> about Io but if one wanted to know the weight <em>W'</em> of the watermelon there one just have to do:

Yes, Sliding friction opposes the movement of the book, slowing it down.sliding That's the 'kinetic' kind.. According to Newton's second law, F=ma. That is, the bear's acceleration should be proportional to the total force acting on the bear. As the bear's velocity is constant, its acceleration is zero. Therefore, the total Force acting on the bear is zero. Thus, the friction has to be equal in magnitude and opposite in direction to the bear's weight. As W=mg, we get that its weight is <span>9.8*400=3,920 Newton. Thus, the friction acting on the bear is 3,920 Newton</span>