Which topic are you most likely to find in a physics textbook?
1 answer:
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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.
Answer:
The decrease in decibels is 0.1 dB.
Explanation:
Let the intensity of one chorus is Io.
let the intensity of 1000 vocalist is dB.
The intensity of 1000 vocalist is 1000 Io.
..... (1)
let the intensity of 999 vocalist is dB'.
..... (2)
So, the change is
= dB - dB' = 30 - 29.9 = 0.1 dB