<span>Since the trains area headed in completely opposite directions, the rate at which they gain distance from each other is simply equal to the sum of the magnitudes of their velocities, in this case 85 + 75 = 160 miles per hour. Therefore, the amount of time it will take for them to be 352 miles apart is 352/160 = 2.2 hours, or 2 hours and 12 minutes.</span>
Well, half-life is the radioactivity of an identified isotope that decreases by half of the actual value.
So, your answer would be C.
There are some missing data in the problem. The full text is the following:
"<span>A </span>real<span> (</span>non-Carnot<span>) </span>heat engine<span>, </span>operating between heat reservoirs<span> at </span>temperatures<span> of 710 K and 270 K </span>performs 4.1 kJ<span> of </span>net work<span>, and </span>rejects<span> 9.7 </span>kJ<span> of </span>heat<span>, in a </span>single cycle<span>. The </span>thermal efficiency<span> of a </span>Carnot heat<span> engine, operating between the same </span>heat<span> reservoirs, in percent, is closest to.."
Solution:
The efficiency of a Carnot cycle working between cold temperature </span>

and hot temperature

is given by

and it represents the maximum efficiency that can be reached by a machine operating between these temperatures. If we use the temperatures of the problem,

and

, the efficiency is

Therefore, the correct answer is D) 62 %.
Wave speed = (wavelength) x (frequency)
Wave speed = (3 m) x (15 Hz)
<em>Wave speed = 45 m/s</em>
smog is a term used to describe air pollution that is a result of the interaction of sunlight with certain chemicals in the atmosphere. One of the primary components of photochemical smog is ozone. While ozone in the stratosphere protects earth from harmful UV radiation, ozone on the ground is hazardous to human health.