<span>Ohm's law deals with the relation between
voltage and current in an ideal conductor. It states that: Potential difference
across a conductor is proportional to the current that pass through it. It is
expressed as V=IR. The correct answer from the choices listed above is option A. The resistance has increased. </span>
Answer: C. good reflector of heat
Explanation:
In space, sunlight transfers heat by radiation to objects and bodies and this includes satellites and astronauts. In addition, although the peak of the sun's emission is in the visible region of the electromagnetic spectrum, a part is also emitted in infrared (transferring thermal energy or heat) and ultraviolet (especially in the upper part of the Earth's atmosphere).
That is why in space missions, objects and many satellites are covered by thin layers or sheets that reflect this thermal energy and thus avoid damaging the equipment due to high temperatures.
In this sense, among the reflective materials used are aluminum, silver, copper and gold; the latter being the most used because it does not corrode or oxidize (unlike silver and copper) and is more malleable than aluminum.
On the other hand, <u>astronauts are also vulnerable to the effects of infrared radiation, especially their eyes</u>, since the human eye has no receptors in the infrared spectrum. <u>That is why the astronaut's helmet visor is covered with a thin layer of gold to avoid the dangerous effects of solar radiation.</u>
The change in internal energy of a system is given by (second law of thermodynamics)
where Q is the heat absorbed by the system and W is the work done on the system.
In order to correctly evaluate the internal energy change, we must be careful with the signs of Q and W:
Q positive -> Q absorbed by the system
Q negative -> Q released by the system
W positive -> W done on the system by the surroundings
W negative -> W done by the system on the surroundings
In our problem, the heat released by the system is
(with negative sign since it is released by the system), and the work done is
still with negative sign because it is performed by the system on the surrounding, so the change in internal energy is
Answer: 2.3m/s
Explanation:
mass-energy balance: ke(f) + pe(f) = ke(o) + pe(o)
since we are looking for the point at the bottom of the pendulum, thats the reference point, the lowest in the system. pe(f) is 0, since h
ke(f)=0.5m x v(f)^2
pe(f)=0
ke(o)=0.5m x v(o)^2
pe(o)-mxgxh
find h by: drawing a triangle with the pendulum at the vertical, then displaced by 25 degrees , The difference in height is h, because cos(25)=(adj)/(hyp)=(2-h)/2. I found h=0.187m
In the m-e balance, cancel the masses in all the terms.
.5xv(f)^2 =0.5v(o)^2 +gxh
Given v(o) = 1.2 m/s and g = 9.8 then v(f) = 2.2595 m/s
Therefore V(0) = 2.3 m/s
<u>C</u> is the correct answer, because energy cannot be created neither destroy. The energy is changing from chemical to from electric to light, and from light to heat.
