Answer:
The time to boil the water is 877 s
Explanation:
The first thing we must do is calculate the external resistance (R) of the circuit, from the description we notice that it is a series circuit, by which the resistors are added
V = i (r + R)
We replace we calculate
r + R = V / i
R = v / i - r
R = 10/12 -0.04
R = 0.793 Ω
We calculate the power supplied
P = V i = I² R
P = 12² 0.793
P = 114 W
This is the power dissipated in the external resistance
We use the relationship, that power is work per unit of time and that work is the variation of energy
P = E / t
t = E / P
t = 100 10³/114
t = 877 s
The time to boil the water is 877 s
Answer:
The airspeed must be 7.78 m/s for the rectangular plate kept at 30°.
Explanation:
By looking at the images below wee see that the airspeed on one side of the rectangular plate decreases the statical pressure over this side. Since over the downside, the pressure still bein the atmospheric pressure. This difference in pressure produces a lift force in the plate. The list force is the net force obtained between the difference of the forces that produce the pressure over the upside and the downside:

Where up and down relate to what movement the forces produce. And p and V are the respective air density and velocity.
When the plate is kept horizontal the lift force balance the moment due to the weight of the plate and considering that both forces act at the same point:

By replacing the known values it is possible to find the plate's weight:


When the plate kept to 30° from the vertical the moment equation balance is written as:

The sine of 30° is due to the weight is 30° oriented, therefore the new value for the airspeed is:






The elements that is very good in
electrical conductivity are gold and copper: elements that is amphoteric are
copper, zinc, tin, lead, aluminum and beryllium: elements that is gaseous at
room temperature are hydrogen, nitrogen, oxygen, fluorine and chlorine: elements
that is solid at room temperature are all metal except mercury and perhaps some
unseen radioactive elements. Lastly, elements that is brittle are hydrogen,
carbon, nitrogen, oxygen, phosphorus, sulfur and selenium