Answer:
As a substance reaches the melting point, the particles begin to move faster, causing the substance to become a liquid.
Explanation:
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Answer:

Explanation:


If the sun considered as x=0 on the axis to put the center of the mass as a:

solve to r1


Now convert to coordinates centered on the center of mass. call the new coordinates x' and y' (we won't need y'). Now since in the sun centered coordinates the angular momentum was

where T = orbital period
then L'(x',y') = L(x) by conservation of angular momentum. So that means

Since
then

Answer: D Although the total energy remains constant, nonrenewable fuels convert chemical energy into forms that are difficult or impossible to use again.
Explanation:
The first law of thermodynamics says that energy can neither be created nor destroyed; energy can only be transferred or changed from one form to another.
Answer:
lead with Z = 82 is transformed into Bismuth with Z = 73
The Po with Z = 84 becomes Pb with Z = 82
Explanation:
Beta decay occurs when a neutron emits an electron and an anti neutrino from the atomic nucleus, therefore the atomic number of the material increases by one unit.
Pb + e + ν → Bi
lead with Z = 82 is transformed into Bismuth with Z = 73
In alpha decay, a helium nucleus is emitted from the nucleus of the atom, therefore the atomic number decreases by two units.
Po +α → Pb
The Po with Z = 84 becomes Pb with Z = 82