Motion of a particle and zero velocity

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The motion of a particle is defined by the equation x = 2t^3 - 15t^2 + 24t + 4, where x is in meters and t in seconds. To determine when the velocity is zero, the derivative of the position function must be calculated and set to zero. The acceleration is also derived from the position function, and its zero points indicate when the particle changes direction. The total distance traveled is calculated by evaluating the position at critical points and summing the absolute values of the displacements. The final distance traveled by the particle is confirmed to be 24.5 meters.
Alexanddros81
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Homework Statement


11.7 The motion of a particle is defined by the relation ##x = 2t^3 - 15t^2 + 24t + 4
where x is expressedin meters and t in seconds. Determine (a) when the velocity zero ,
(b) the position and the total distance traveled when the acceleration is zero

Homework Equations

The Attempt at a Solution



Vector Mechanics Dynamics Beer P11_7 s.jpg

[/B]
Can you check if my solution is correct?
 

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Alexanddros81 said:

Homework Statement


11.7 The motion of a particle is defined by the relation ##x = 2t^3 - 15t^2 + 24t + 4
where x is expressedin meters and t in seconds. Determine (a) when the velocity zero ,
(b) the position and the total distance traveled when the acceleration is zero

Homework Equations

The Attempt at a Solution



View attachment 222710
[/B]
Can you check if my solution is correct?
First, let me comment that your printing is neat and readable in the image. However, you are much more likely to get responses to your questions if you type in your solution. Many helpers will not respond otherwise.

That said, yes, your solution looks correct.
 
Looks good to me.
 
Is my last sentence correct?

I think it should be ##x(2.5) - x(1) = 1.5 - 15 = -13.5## (moving in opposite direction).
Overall though the particle travels a total distance of 11+13.5 = 24.5
 
The book claims the answer is that all the magnitudes are the same because "the gravitational force on the penguin is the same". I'm having trouble understanding this. I thought the buoyant force was equal to the weight of the fluid displaced. Weight depends on mass which depends on density. Therefore, due to the differing densities the buoyant force will be different in each case? Is this incorrect?

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