An object of mass 5 kg falls from rest through a vertical distance of `20 m` and attains a velocity of 10 m/s. How much work is done by the resistance of the air on the objrct? `(g=10m//s^(2))`.
Text Solution
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Applying work-energy theorem, work done by all the forces =change in kinetic energy or `W_mg+W_"air"=1/2mv^2-mv` `:. W_"air"=1/2mv^2-W_mg=1/2mv^2-mgh` `=1/2xx5xx(10)^2-(5)xx(10)xx(20)` `=-750j`
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