Calculating Time for 1000kg Boat to Slow from 90km/h to 45km/h

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To determine the time required for a 1000kg boat to decelerate from 90km/h to 45km/h after the engine is shut off, the frictional force acting on the boat, which is proportional to its speed (fk = 70v), must be considered. Using Newton's second law, the relationship between velocity and acceleration can be established as dv/dt. A differential equation can then be solved to find the time taken for the boat to slow down. The discussion also touches on the need for clarity in using mathematical templates for posting such questions. Properly applying these principles will yield the desired time calculation.
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A 1000kg boat is traveling at 90km/h when its engine is shut off. The magnitude of frictional force fk between boat and water is proportional to the speed v of the boar: fk=70v, where v is in meters per second and fk is in Newtons. find the time required for the boat to slow to 45km/h.

The question does not ask for acceleration, so do I need to find the acceleration before finding the time?

In addition, Does anyone knows how to use a math template for posting this type of question?

Thanks,
 
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Any thought on it would be fine, thanks.
 
Use Newton's second law to get the relation between velocity v and acceleration, dv/dt. Solve the differential equation.

ehild
 

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