The amount of work that has been done on the projectile by air friction is 7,569.2 J.
The work done by air friction on the projectile is calculated as follows;
W = ΔK.E
W = ¹/₂mvf² - ¹/₂mv₀²
where;
W = ¹/₂m(vf² - v₀²)
W = ¹/₂ x 2.5 (85² - 34.2²)
W = 7,569.2 J
Thus, the amount of work that has been done on the projectile by air friction is 7,569.2 J.
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