Sifting is the best method cuz all the dirt will be carried by wind.
The answer is believed to be C because the evidence is from fossils and glaciers.
W = mg
Weight on Earth = 50 x 9.8
= 490 N
Weight on Mars = 50 x 3.7
= 185 N
The block is made of A) Tin, as its specific heat capacity is 
Explanation:
When an amount of energy Q is supplied to a sample of material of mass m, the temperature of the material increases by 
, according to the following equation
:
where 
is the specific heat capacity of the material.
In this problem, we have:
m = 2 kg = 2000 g is the mass of the unknown material
is the amount of energy supplied to the block
is the change in temperature of the material
Solving the equation for , we can find the specific heat capacity of the unknown sample:
And by comparing with tabular values, we can find that this value is approximately the specific heat capacity of tin.
Learn more about specific heat capacity:
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Thank you for your question, what you say is true, the gravitational force exerted by the Earth on the Moon has to be equal to the centripetal force.
An interesting application of this principle is that it allows you to determine a relation between the period of an orbit and its size. Let us assume for simplicity the Moon's orbit as circular (it is not, but this is a good approximation for our purposes).
The gravitational acceleration that the Moon experience due to the gravitational attraction from the Earth is given by:
ag=G(MEarth+MMoon)/r2
Where G is the gravitational constant, M stands for mass, and r is the radius of the orbit. The centripetal acceleration is given by:
acentr=(4 pi2 r)/T2
Where T is the period. Since the two accelerations have to be equal, we obtain:
(4 pi2 r) /T2=G(MEarth+MMoon)/r2
Which implies:
r3/T2=G(MEarth+MMoon)/4 pi2=const.
This is the so-called third Kepler law, that states that the cube of the radius of the orbit is proportional to the square of the period.
This has interesting applications. In the Solar System, for example, if you know the period and the radius of one planet orbit, by knowing another planet's period you can determine its orbit radius. I hope that this answers your question.
