Answer:
12.6 cm
Explanation:
We can use the mirror equation to find the distance of the image from the mirror:

where here we have
f = 9.50 cm is the focal length
p = 39 cm is the distance of the object from the mirror
Solving the equation for q, we find:

Answer:
The change in temperature is
Explanation:
From the question we are told that
The temperature coefficient is 
The resistance of the filament is mathematically represented as
![R = R_o [1 + \alpha \Delta T]](https://tex.z-dn.net/?f=R%20%20%3D%20%20R_o%20%5B1%20%2B%20%5Calpha%20%20%5CDelta%20T%5D)
Where
is the initial resistance
Making the change in temperature the subject of the formula
![\Delta T = \frac{1}{\alpha } [\frac{R}{R_o} - 1 ]](https://tex.z-dn.net/?f=%5CDelta%20T%20%3D%20%5Cfrac%7B1%7D%7B%5Calpha%20%7D%20%5B%5Cfrac%7BR%7D%7BR_o%7D%20-%201%20%5D)
Now from ohm law

This implies that current varies inversely with current so

Substituting this we have
![\Delta T = \frac{1}{\alpha } [\frac{I_o}{I} - 1 ]](https://tex.z-dn.net/?f=%5CDelta%20T%20%20%3D%20%5Cfrac%7B1%7D%7B%5Calpha%20%7D%20%5B%5Cfrac%7BI_o%7D%7BI%7D%20-%201%20%5D)
From the question we are told that

Substituting this we have
![\Delta T = \frac{1}{\alpha } [\frac{I_o}{\frac{I_o}{8} } - 1 ]](https://tex.z-dn.net/?f=%5CDelta%20T%20%20%3D%20%5Cfrac%7B1%7D%7B%5Calpha%20%7D%20%5B%5Cfrac%7BI_o%7D%7B%5Cfrac%7BI_o%7D%7B8%7D%20%7D%20-%201%20%5D)
=> 
780 seconds, or 13 minutes.
In the future, please use proper capitalization. There's a significant difference in the meaning between mV and MV. One of them indicated millivolts while the other indicates megavolts. For this problem, I'll make the following assumptions about the values presented. They are:
Total energy = 1.4x10^11 Joules (J)
Current per flash = 30 Columbs (C)
Potential difference = 30 Mega Volts (MV)
First, let's determine the power discharged by each bolt. That would be the current multiplied by the voltage, so
30 C * 30x10^6 V = 9x10^8 CV = 9x10^8 J
Now that we know how many joules are dissipated per flash, let's determine how flashes are needed.
1.4x10^11 / 9x10^8 = 1.56E+02 = 156
Since each flash takes 5 seconds, that means that it will take about 5 * 156 = 780 seconds which is about 780/60 = 13 minutes.