Force = -kx
80N=0.15m * -k
K=-80/0.15=533.333. Spring constant
Energy=1/2kx^2
1/2*(-80/0.15)*80^2=Energy
The answer is B.
A cannot be the answer is melting is a physical change. No chemical reaction took place.
B is the answer as it is a EXOTHERMIC REACTION so heat will be given off.
C cannot be the answer as dissolving is basically atoms becoming ions, not a chemical reaction whereby a reactant reacts with another reactant to form a product.
D cannot be the answer. Same reason as for why A is not the answer.
Cheers.
The distance for any rectilinear motion at constant acceleration is:
d = v₀t + 0.5at²
where
v₀ is the initial velocity
So, if v₀ = 6v, and it stopped to 0 m/s, then the acceleration is equal to:
a = (0 - 6v)/t = -6v/t
Thus,
d = (6v)(t) + (0.5)(-6v/t)(t²)
d = 6vt - 3t
<span>d = 3t(2v - 1)</span>
The half-life of a substance describes the time in which it takes for half of the radioactive isotope to decay into another form. In your question, it says that the half life of radon-222 is 3.82 days; in a 100g sample of radon, 3.82 days pass and 50g of that isotope is left.
7.64 days is the equivalent to two half lives (7.64/3.82), so only half of half of 100%, or 25%, of the isotope would remain. The answer is D
Hope that helps
