Engineering Board Exam Reviewer · Applications: Newton's Second Law and Motion · medium
A 500-kg boat moving at 10 m/s shuts off its engine. The water resistance is 50v newtons. How far does the boat travel while its speed drops to 2 m/s?
- 100 m
- 80 m
- 20 m
- 40 m
Answer
B. 80 m
Solution
mdv/dt=-50v and dv/dt=vdv/dx, so 500,dv=-50,dx x=500/50(10-v). At v=2: x=10(8)=80 m.
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