__Question__:

A moving 4.5 kg block collides with a horizontal spring whose spring constant is 424 N/m (see figure). The block compresses the spring a maximum distance of 13.0 cm from its rest position. The coefficient of kinetic friction between the block and the horizontal surface is 0.36. (a) What is the work done by the spring in bringing the block to rest?

(a) 0.564668J (THIS ANSWER IS WRONG)

$\displaystyle \textcolor{red}{|W_s| = \frac{1}{2}kx^2}$

(b) How much work was done by the force of friction (non-conservative force = Wnc) while the block is being brought to rest by the spring?

(b) -2.06388J (THIS ANSWER IS CORRECT)

(c) What is the speed of the block when it hits the spring?

$\displaystyle \textcolor{red}{KE = \frac{1}{2}mv^2 = |W_s| + |W_f|}$

(c) 0.50096 m/s (THIS ANSWER IS WRONG)