What is the velocity of a decelerating boat after 4.9 seconds?

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SUMMARY

The discussion focuses on calculating the velocity of a decelerating boat after 4.9 seconds, starting with an initial velocity of 9.9 m/s and decelerating at a rate defined by a=-kv², where k=5.5 m. The correct approach involves recognizing the equation as a separable differential equation and integrating both sides appropriately. The final velocity can be determined by integrating from the initial velocity to the final velocity over the specified time interval, leading to a successful resolution of the problem.

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  • Understanding of separable differential equations
  • Knowledge of basic calculus, specifically integration techniques
  • Familiarity with the concept of deceleration and its mathematical representation
  • Ability to manipulate and solve equations involving initial conditions
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  • Study the method of integrating separable differential equations in detail
  • Learn about the physical implications of quadratic deceleration in motion
  • Explore more complex applications of differential equations in physics
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Students studying physics, particularly those focusing on mechanics and differential equations, as well as educators looking for examples of real-world applications of calculus in motion problems.

Lenart Kovac

Homework Statement


A boat, moving at the velocity of 9,9m/s turns off its engine and starts decelerating at the rate of a=-kv^2. What is the velocity of the boat after 4,9 seconds if the constant k is k=5,5m

Homework Equations

The Attempt at a Solution


I tried to integrate deceleration to get velocity, which got me the equation v= -k * t * v0^2, but that got me a really weird number and I'm sure I'm not doing something right, so I'm asking you for help
 
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This is a separable differential equation. The way you need to integrate is like this: First, note that a = dv/dt, so we have dv/dt = -k*v2.
Rearrange so that you have this
$$dt = \frac {dv} {-k v^2},$$
Now you can integrate both sides. If you don't want to fool with integration constant, then you can integrate the right side (with velocity) from 9.9 m/s to vf and integrate the left side (time) from 0 seconds to 4.9 seconds. Then you can rearrange to solve for vf
 
Last edited:
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I made a revision, it seems I had my left side and right side switched around :eek: Also I used some LateX so it would look a little nicer.
 
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It worked! Thanks for the help :)
 

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