Engineering Board Exam Reviewer · Applications: Newton's Second Law and Motion · medium
A 2-kg object is dropped from rest and falls under gravity (g=9.81 m/s2) against an air resistance of 4v newtons, where v is its speed in m/s. Find its speed after 1 second.
- 4.24 m/s
- 4.82 m/s
- 4.91 m/s
- 3.1 m/s
Answer
A. 4.24 m/s
Solution
mdv/dt=mg-4v /dt=9.81-2v. With v(0)=0: v=4.905≤ft(1-e-2t ). At t=1: v=4.905(1-e-2) 4.24 m/s.
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