A 900-kg boat is travelling at 70 km/hr when its engine is shut off the magnitude of the feraction force Fk between the boat and water is peroportional to the speed of the boat by Fk=-30v where v is in m/s and Fk in N find the time required for the boat to slow dawn to 35 km/hr
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Answer: 20.79 hours
Explanation:
fk = mass of the boat x a (where a is the acceleration)
=> -30v = 900a
=> a = v / 30
=> dv/dt = v / 30
=> dt = (30 / v)dv
Integrating both sides, with limits on t being 0 to t and limits on v being 70 to 35, we get,
t = (30)(ln70 - ln35)
= 30 × 0.693
= 20.79 h
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