The power used by Alex to drag the log across the yard is determined as 2,656 W.
<h3>Mass of the log</h3>
The mass of the log is calculated as follows;
W = mg
m = W/g
m = (400)/9.8
m = 40.82 kg
<h3>Velocity of the log</h3>
K.E = ¹/₂mv²
v² = 2K.E/m
v² = (2 x 900)/(40.82)
v² = 44.096
v = 6.64 m/s
<h3>Power used by Alex</h3>
P = Fv
P = 400 x 6.64
P = 2,656 W
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Explanation:
Since, it is given that carbon dioxide is completely removed by absorption with NaOH. And, pressure inside the container is 0.250 atm.
For Kr = 0.250 atm and pressure
will be calculated as follows.
= (0.708 - 0.250) atm
= 0.458 atm
Now, we will calculate the mole fraction as follows.

= 0.646
Kr = 
= 0.353
Now, we will convert into gram fraction as follows.

= 28.424
Kr = 
= 29.57
Therefore, total mass is calculated as follows.
Total mass = (28.424 + 29.57)
= 57.994
Hence, the percentage of
and Kr are calculated as follows.

= 49%
Kr = 
= 51%
Hence, amount of
and Kr present i mixture is as follows.
in mixture = 
= 17.15 g
Kr = 
= 17.85 g
Thus, we can conclude that 17.15 g of
is originally present and 17.85 g of Kr is recovered.