Calculating Distance and Time given mass,velocity,and Force.

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Homework Help Overview

The discussion revolves around a physics problem involving a power boat's motion, specifically calculating distance and time given its mass, velocity, and force. The scenario describes a boat coasting to a halt after the engine is turned off, with a focus on the forces acting on it.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to calculate acceleration using the formula F=ma and subsequently uses that to find time and distance. Some participants question the correctness of the acceleration calculation and suggest looking into kinematics equations. Others express confusion about how to find acceleration without knowing distance and time.

Discussion Status

The discussion is ongoing, with participants exploring different interpretations of the problem. Some guidance has been offered regarding the use of kinematics equations, but there is no explicit consensus on the correct approach yet.

Contextual Notes

There is an assumption that the resistive force is constant, which may not reflect real-world conditions. The original poster's calculations have been challenged, indicating potential misunderstandings in applying the relevant physics concepts.

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Homework Statement


A power boat of mass 475 kg is cruising at a constant speed of 8.9 m/s. The propeller provides a drive force of 765 N. The driver of the boat shuts off the engine, and the boat coasts to a halt. Assume-contrary to fact-that the resistive force due to the water is constant, independent of the boat's speed.

Homework Equations


F=ma
a=velocity/time
v=d/t

The Attempt at a Solution


I divided Force by mass to get acceleration since F=ma.
Then using the acceleration formula a=d/t i calculated time.
Using that time i calculated distance useing the velocity formula v=d/t.
I got 49.183 meters and 5.526 seconds.
I got this answer wrong.
 
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Your formula for acceleration is not correct. Look up the "kinematics equations" to get the time and the distance. You'll need to think about the boat's final velocity to use one of the kinematics equations.
 
but i can't figure out how to calculate acceleration because i need distance and time.
 
you already said how to find acceleration! F = ma!
 
thank you very much!
 

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