Physics - work done by a spring

AI Thread Summary
The discussion centers on calculating the work done by a spring when a block compresses it after a collision. The block, weighing 4.90 kg, compresses the spring with a constant of 437 N/m by 6.50 cm. The correct formula for work done by the spring is W = -0.923 J, indicating that the work is negative due to the spring's opposing force. Participants noted that while the work done by friction was correctly calculated as -0.594 J, there was confusion about the signs used in the calculations. Ultimately, the consensus confirms that the work done by the spring should indeed be negative, aligning with the principles of energy conservation.
Felix83
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A moving 4.90 kg block collides with a horizontal spring whose spring constant is 437 N/m.

The block compresses the spring a maximum distance of 6.50 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.190. What is the work done by the spring in bringing the block to rest?

The Part after that is to find the work done by friction, which I got correct. The last part is to find the initial velocity of the block, I could just add the work done by friction and the spring and then solve for v with the KE formula.

However, I can't seem to find the work done by the spring to bring the block to rest. Wouldn't you just use the formula W=(1/2)kx^2 ? I used that and got 0.923 J, which the program says is incorrect.
 
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Obviously there has to be a minus in the result,so it should be -0.923J.Indeed,to me,that seems to be the answer,the dork done by the elastic force acting on the body is - the elastic potential energy...
Weird,maybe something is evading my senses,but,for now,i'd say that's the correct result.

Daniel.
 
Appears that {Work Done By Spring}=(-0.923 J), {Work Done by Friction}=(-0.594 J), and {Initial Velocity}=(+0.787 m/sec) should be correct.

~~
 
yea those are the numbers i got too, but i put the friction in as positive and it said correct so i figured since the spring was pushing in the same direction it would be positive too. but these problems are dumb sometimes so i tried negative 0.923 and of course that was right.
 

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