Answer:
The time rate of change in air density during expiration is 0.01003kg/m³-s
Explanation:
Given that,
Lung total capacity V = 6000mL = 6 × 10⁻³m³
Air density p = 1.225kg/m³
diameter of the trachea is 18mm = 0.018m
Velocity v = 20cm/s = 0.20m/s
dv /dt = -100mL/s (volume rate decrease)
= 10⁻⁴m³/s
Area for trachea =

0 - p × Area for trachea =



⇒

ds/dt = 0.01003kg/m³-s
Thus, the time rate of change in air density during expiration is 0.01003kg/m³-s
Answer:
Pressure difference between Top and Bottom of the cylinder is given as

Explanation:
As we know that the force due to pressure is balanced by the weight of the cylinder
So we will have

so we have

so we have

so we have

Answer:
During convection, hot material expands & rises then moves to the side and cools & sinks. this circular pattern is called a convection current.
Explanation:
Convection is one of the three methods of transfer of heat. It occurs only in fluids (liquids or gases).
Convection occurs when there is a source of heat that heats a fluid, such as in a boiling pot of water. The water which is on the bottom of the pot becomes warmer before than the water at the top (because it is closer to the flame), and so it becomes less dense: for this reason, it expands and it becomes rising. On the contrary, the water on top is colder, so it is more dense and starts sinking, replacing the warmer water. As the new part of water gets warmer, it starts rising, and so the process is continuously repeated. This circular current is called convection current.
Answer: The direction of the electric field, E→, is pointed in the +y direction.
Explanation:
One can use the right hand rule to illustrate the direction of travel of an electromagnetic and thereby get the directions of the electric field, magnetic field and direction of travel of the wave.
The right hand rule states that the direction of the thumb indicate the direction of travel of the electromagnetic wave (<em>in this case the -z direction</em>) and the curling of the fingers point in the direction of the magnetic field B→ (<em>in this case the +x direction</em>), therefore, the electric field direction E→ is in the direction of the fingers which would be pointed towards the +y direction.
Answer:
t = 23136 years old
Explanation:
The intensity of radiation obeys the exponential decay law.
(1)
Here:
λ is the radiation decay constant.
I is the intensity of radiation after t time.
I₀ is the initial intensity of radiation.
t is the time
Now, we know that the intensity of radiation is a 6% of what it would be in a freshly cut piece of wood, in other words:
(2)
Combining (2) with (1), we have:

(3)
Now, we just need to solve (3) for t.
(4)
and
(5)
is the half-life.
In our case, we have ¹⁴C, so the 
Finally, we can find t putting (5) in (4):

I hope it helps you!