Show that acceleration varies as cube of the distance given

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The discussion presents a mathematical approach to demonstrate that acceleration varies as the cube of the distance. The relationship starts with distance represented as x and velocity as x', leading to the equation x' = kx^2, where k is a constant. The acceleration is derived as x'' = 2k(x)(x'), which simplifies to x'' = 2k^2x^3. This indicates that acceleration is proportional to the cube of the distance, confirming the initial premise. The calculations appear to be correct and consistent with the proposed relationship.
chwala
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Homework Statement
See attached.
Relevant Equations
Rate of change
1698409888454.png


In my approach i have distance as ##(x)## and velocity as ##(x^{'})##, then,

##(x^{'}) = kx^2##

where ##k## is a constant, then acceleration is given by,

##(x^{''}) = 2k(x) (x^{'})##

##(x^{''}) = 2k(x)(kx^2) ##

##(x^{''}) = 2k^2x^3##.

Correct?
 
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It seems OK.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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