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<span>a=Δω/Δt
</span><span>a=2π*Δf/Δt
</span><span>a=2π*(f2-f1)/Δt
</span>
<span>f1=f2-a*Δt/2π
</span><span>f2=800/60 rev/sec
</span><span>a=-42 rad/sec^2
</span><span>Δt=1.75sec
</span><span>so
f1=25 rev/sec
f1=1500 rev/min</span>
The aspect of his fitness program that could keep the young man from achieving his goal would potentially be the exercise with his friend. His friend could be a hindrance to his motivation to do more or to continue. If he's so attached with exercising with his friend and his friend decides to stop, then he would probably lose motivation.
The answer is C. I just took the test.
I hope this helps. :)