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1 answer:
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Answer:
0.5 g
Explanation:
The half-life of a radioactive isotope is the time it takes for a certain amount of that isotope to halve.
In this case, we have an isotope of Americium-241, which has a half-life of
This means that after 1 half-life (432 years), there will be an amount of americium equal to half its initial amount.
In this problem, the initial amount of americium is
Therefore, after 432 years (1 half-life), the amount of americium left will be half:
Answer:
4.15 m/s
Explanation:
As the total energy must be conserved (neglecting air resistance) the change in gravitational potential energy, must be equal to the change in kinetic energy:
ΔE = ΔK + ΔU =0
If we take as a zero reference level for the gravitational potential energy, the height of the swing seat above the ground, (which is equal to 0.21 m), we can find the initial gravitational energy, considering the height of the point where the seat is released, regarding this point:
h₀ = 1.09 m -0.21 m = 0.88 m
⇒ U₀ = m*g*h₀ = 400 N*0.88 m = 352 J
As Uf = 0, ΔU = Uf -U₀ = -352 J
As the swing starts from rest, K₀=0, so we can say:
ΔK = Kf = (1)
As ΔK = -ΔU ⇒ ΔK = 352 J (2)
From (1) and (2) we can solve for vf, as follows:
So, when the swing passes through its lowest position, Betty moves at 4.15 m/s.