There are two ways to find energy. Energy=F*d=mv^2. We can use this relationship to find v:
Answer:
460.52 s
Explanation:
Since the instantaneous rate of change of the voltage is proportional to the voltage in the condenser, we have that
dV/dt ∝ V
dV/dt = kV
separating the variables, we have
dV/V = kdt
integrating both sides, we have
∫dV/V = ∫kdt
㏑(V/V₀) = kt
V/V₀ = ![e^{kt}](https://tex.z-dn.net/?f=e%5E%7Bkt%7D)
Since the instantaneous rate of change of the voltage is -0.01 of the voltage dV/dt = -0.01V
Since dV/dt = kV
-0.01V = kV
k = -0.01
So, V/V₀ = ![e^{-0.01t}](https://tex.z-dn.net/?f=e%5E%7B-0.01t%7D)
V = V₀![e^{-0.01t}](https://tex.z-dn.net/?f=e%5E%7B-0.01t%7D)
Given that the voltage decreases by 90 %, we have that the remaining voltage (100 % - 90%)V₀ = 10%V₀ = 0.1V₀
So, V = 0.1V₀
Thus
V = V₀![e^{-0.01t}](https://tex.z-dn.net/?f=e%5E%7B-0.01t%7D)
0.1V₀ = V₀![e^{-0.01t}](https://tex.z-dn.net/?f=e%5E%7B-0.01t%7D)
0.1V₀/V₀ = ![e^{-0.01t}](https://tex.z-dn.net/?f=e%5E%7B-0.01t%7D)
0.1 = ![e^{-0.01t}](https://tex.z-dn.net/?f=e%5E%7B-0.01t%7D)
to find the time, t it takes the voltage to decrease by 90%, we taking natural logarithm of both sides, we have
㏑(0.01) = -0.01t
So, t = ㏑(0.01)/-0.01
t = -4.6052/-0.01
t = 460.52 s
The element is iridium and it has 77 electrons
Answer:
Option d is correct.
Explanation:
We know , resistance of a body is directly proportional to its length and inversely proportional to its area.
( Here,
is constant dependent on object material )
Writing
also :
( since they are of same material therefore,
is same.)
Now , if
.
Then ![R_1=R_2](https://tex.z-dn.net/?f=R_1%3DR_2)
Therefore, option d. is correct.
Hence, this is the required solution.