A student uses a compressed spring of force constant 22 N/m to shoot a 0.0075 kg eraser across a desk. The magnitude of the force of friction on the eraser is 0.042 N. How far along the horizontal desk will the eraser slide if the spring is initially compressed 3.5 cm. Use the law of conservation of energy. i think you have to find acceleration first but it doesnt make sense when i do it. I end up 97 m/s. Heres what i did. Fnet=Fe-Ff But i think thats wrong. so can anyone please help me.