Answer:
B. QC > 0; QH < 0
Explanation:
Given that there are two reservoir of energy.
Sign convention for heat and work :
1.If the heat is adding to the system then it is taken as positive and if heat is going out from the system then it is taken as negative.
2. If the work is done on the system then it is taken as negative and if the work is done by the system then it is taken as positive.
From hot reservoir heat is going out that is why it is taken as negative

From cold reservoir heat is coming inside the reservoir that is why it is taken as positive

That is why the answer will be
,
Answer:
r = 58.44 [m]
Explanation:
To solve this problem we must use the following equation that relates the centripetal acceleration with the tangential velocity and the radius of rotation.
a = v²/r
where:
a = centripetal acceleration = 15.4 [m/s²]
v = tangential speed = 30 [m/s]
r = radius or distance [m]
r = v²/a
r = 30²/15.4
r = 58.44 [m]
Answer: piece of paper cut into a triangle
Explanation:
A plane surface lifted at an angle to horizontal from one edge is said to be an inclined plane. A wedge, a ramp or a screw are examples of a forms of inclined plane. A screw is like a inclined plane wound on a cylinder. These are simple machines. On the other hand, a piece of paper cut into a triangle is not an inclined plane as it does rise at an angle from horizontal. It is not a machine.
The concept required to solve this problem is related to the wavelength.
The wavelength can be defined as the distance between two positive crests of a wave.
The waves are in phase, then the first distance is

And out of the phase when

Thus the wavelength is

Here,
Wavelength
If we rearrange the equation to find it, we will have



Therefore the wavelength of the sound is 20cm.