Find the time required for the boat to slow to 45 km/hr

  • Thread starter king_naeem
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  • #1
hey

A 1000 kg boat is travelling at 90km/h when its engine is shut off. The magnitude of the frictional force between boat and water is proportional to the speed v of the boat: force of kinetic fricition=70v, where v is in meters per second and the force is in newtons. Find the time required for the boat to slow to 45 km/hr
 

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dextercioby
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king_naeem said:
hey

A 1000 kg boat is travelling at 90km/h when its engine is shut off. The magnitude of the frictional force between boat and water is proportional to the speed v of the boat: force of kinetic fricition=70v, where v is in meters per second and the force is in newtons. Find the time required for the boat to slow to 45 km/hr

I'm a theorist,so i'll let u plug the numbers:
The Newton's law states:[itex] m\frac{dv}{dt}=-\alpha v [/itex],where alpha is that 70 in your problem:
Integrate the ODE wrt to proper limits:
Final result:[itex] t=(\frac{1000}{70}\ln 2) s [/itex]

Good luck!!
 

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