Answer:

Explanation:
Given:
Initial mass of isotope (m₀) = 20 g
Half life of the isotope
= (ln 4) years
The general form for the radioactive decay of a radioactive isotope is given as:

Where,

So, the equation is: 
At half-life, the mass is reduced to half of the initial value.
So, at
. Plug in these values and solve for 'k'. This gives,

Hence, the equation for the mass remaining is given as:

Answer:
Applying 200 N of force to the chair from the right
Explanation:
Coefficient of performance or more commonly known as COP is calculated through the equation,
COP = ((T₂)/(T₂ - T₁))
where T₂ is the hot temperature and T₁ is the cold temperature. Similarly, these can also be,
COP = heat ejected / (heat ejected - heat provided)
Substituting,
COP = 22,000 / (22,000 - 15,000) = 3.14
Thus, the value of the COP is approximately 3.14.
Answer:
A
Explanation:
blue stars have a hotter sufarce arra, thats what makes them brighter.