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Fritz Strobl thrilled the world when he won the gold medal in the Salt Lake City games of 2002 in a daring run down an alpine skiing course. The course had a vertical drop of 880 meters. Assume his highest speed was 140 km/h, and that he was moving at that speed at the end. (a) How fast would he have been moving if he could have "ignored" forces like air resistance and friction? (b) How much energy did he lose to forces like air resistance, friction, and so forth (assume his mass is 80 kg, and express the answer as a positive number)?

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Answer:

131.39863 m/s

683205.94 Joules

Explanation:

m = Mass of person = 80 kg

g = Acceleration due to gravity = 9.81 m/s²

h = Height of the drop = 880 m

v = Speed

[tex]v_m[/tex] = Maximum speed = 140 km/h

Here the Potential and Kinetic energies are conserved

[tex]P_i=K_f\\\Rightarrow mgh=\frac{1}{2}mv^2\\\Rightarrow v=\sqrt{2gh}\\\Rightarrow v=\sqrt{2\times 9.81\times 880}\\\Rightarrow v=131.39863\ m/s[/tex]

The velocity of Fritz Strobl is 131.39863 m/s

Taking friction into consideration

[tex]P_i=W_f+K_f\\\Rightarrow mgh=W_f+\frac{1}{2}mv_m^2\\\Rightarrow W_f=mgh-\frac{1}{2}mv_m^2\\\Rightarrow W_f=80\times 9.81\times 880-\frac{1}{2}\times 9.81\times \frac{140}{3.6}^2\\\Rightarrow W_f=683205.94\ J[/tex]

The work done by friction is 683205.94 Joules

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