Extension in Spring Homework: Find x

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SUMMARY

The discussion focuses on solving a physics homework problem involving the extension of a spring when a block is dropped onto it. The initial calculations determined the spring constant (k = 200) and the velocity of the block (3 m/s) using the formula for gravitational potential energy. However, the final extension of the spring (x = 4.5 cm) was incorrect due to the omission of gravitational potential energy (GPE) loss during the spring's extension. The correct formula incorporating GPE is provided, leading to the correct answer of 6.1 cm.

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Homework Statement


attachment.php?attachmentid=32924&stc=1&d=1299767447.jpg



The Attempt at a Solution



first using the initial extension i found out that k = 200.

velocity of block = √(2gh) = √(2*10*.45) = 3

then using conservation of momentum ...

120 * 3 = 320 * V
V = 1.125

this kinetic energy converts into potential energy of spring

.5 * .32 * V = .5 * 200 * x
x = 4.5 cm

but answer is given as 6.1 cm
 

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You haven't taken into account the gravitational potential energy, GPE is lost by both masses as the spring extents from equilibrium.


[tex] <br /> \frac{1}{2} m v^2=\frac{1}{2}kx^2 -mgx<br /> [/tex]
 
Thanks for your help ... :)
 

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