Which amplitude of the following longitudinal waves has the greatest energy?
amplitude = 10 cm; wavelength = 6 cm; period = 4 seconds
Answer:
ºC
Explanation:
First, let's write the energy balance over the duct:

It says that the energy that goes out from the duct (which is in enthalpy of the mass flow) must be equals to the energy that enters in the same way plus the heat that is added to the air. Decompose the enthalpies to the mass flow and specific enthalpies:

The enthalpy change can be calculated as Cp multiplied by the difference of temperature because it is supposed that the pressure drop is not significant.

So, let's isolate
:

The Cp of the air at 27ºC is 1007
(Taken from Keenan, Chao, Keyes, “Gas Tables”, Wiley, 1985.); and the only two unknown are
and Q.
Q can be found knowing that the heat flux is 600W/m2, which is a rate of heat to transfer area; so if we know the transfer area, we could know the heat added.
The heat transfer area is the inner surface area of the duct, which can be found as the perimeter of the cross section multiplied by the length of the duct:
Perimeter:

Surface area:

Then, the heat Q is:

Finally, find the exit temperature:

=27.0000077 ºC
The temperature change so little because:
- The mass flow is so big compared to the heat flux.
- The transfer area is so little, a bigger length would be required.
Answer:
The magnitude of buoyancy force is equal to that of ball's weight.
Explanation:
Ball 1 is floating on water. Weight of ball 1 is Fg=m1g is acting vertically downward
Force of buoyancy FB = ρVdisg is acting vertically upward.
Net force acting on the ball is zero, FB=Fg
Answer
The magnitude of buoyancy force is equal to that of ball's weight.
Answer:
- The total distance traveled is 28 inches.
- The displacement is 2 inches to the east.
Explanation:
Lets put a frame of reference in the problem. Starting the frame of reference at the point with the 0-inch mark, and making the unit vector
pointing in the west direction, the ant start at position

Then, moves to

so, the distance traveled here is



after this, the ant travels to

so, the distance traveled here is



The total distance traveled will be:

The displacement is the final position vector minus the initial position vector:



This is 2 inches to the east.