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**Linnus** A 10.5 kg block, attached to the left end of a horizontal massless spring, sits on a frictionless table. The right end of the spring is attached to a vertical piece of wood that is firmly nailed to the table. A 0.0500 kg projectile is fired, from left to right, into the block at 85.5 m/s and stops inside it (this is a completely inelastic collision). The spring constant is *k* = 105 N/m. How many meters does the spring compress? The potential energy due to the compression of the spring can be calculated with the following formula: *PE* = (1/2)*kx*^2