1 revolution = 2π radians
revs = (1/2π) · (rads) / (2π)
revs/sec = (1/2π) · (rads/sec)
RPM = (1/2π) · (rads/min) = (30/π) · (rads/sec)
Answer:
The unknown substance is Aluminum.
Explanation:
We'll begin by calculating the change in the temperature of substance. This can be obtained as follow:
Initial temperature (T₁) = 25 ⁰C
Final temperature (T₂) = 100 ⁰C
Change in temperature (ΔT) =?
ΔT = T₂ – T₁
ΔT = 100 – 25
ΔT = 75 ⁰C
Finally, we shall determine the specific heat capacity of the substance. This can be obtained as follow:
Change in temperature (ΔT) = 75 ⁰C
Mass of the substance (M) = 135 g
Heat (Q) gained = 9133 J
Specific heat capacity (C) of substance =?
Q = MCΔT
9133 = 135 × C × 75
9133 = 10125 × C
Divide both side by 10125
C = 9133 / 10125
C = 0.902 J/gºC
Thus, the specific heat capacity of substance is 0.902 J/gºC
Comparing the specific heat capacity (i.e 0.902 J/gºC) of substance to those given in the table above, we can see clearly that the unknown substance is aluminum.
Answer:
31.92 h
Explanation:
We'll begin by calculating the number of half-lives that has elapsed. This can be obtained as follow:
Original amount (N₀) = 1
Amount remaining (N) = ⅛
Number of half-lives (n) =?
N = 1/2ⁿ × N₀
⅛ = 1/2ⁿ × 1
Cross multiply
2ⁿ = 8
Express 8 in index form with 2 as the base.
2ⁿ = 2³
n = 3
Thus, 3 half-lives has elapsed.
Finally, we shall determine the time. This can be obtained as follow:
Half-life (t½) = 10.64 h
Number of half-lives (n) = 3
Time (t) =?
n = t / t½
3 = t / 10.64
Cross multiply
t = 3 × 10.64
t = 31.92 h
Therefore, it will take 31.92 h for lead-212 to decay to one-eighth its original strength.