1. The problem statement, all variables and given/known data The ball launcher in a pinball machine has a spring that has a force constant of 1.2 N/cm. The surface on which the ball moves is inclined at 10° with respect to the horizontal. If the spring is initially compressed 5 cm, find the launching speed of a .1 kg ball when the plunger is released. Friction and the mass of the plunger are negligible. 2. Relevant equations Ue (Elastic potential) = (1/2)kx^2 K (Kinetic) = (1/2)mv^2 Ug (Gravitational potential) = mgh 3. The attempt at a solution k = 1.2 N/ cm = .012 N / m x = 5 cm = .05 m m = .1 kg g = 9.8 m/s Ue = K + Ug .5kx^2 = .5mv^2 + mgh .5(.012)(.05^2) = .5(.1)v^2 + .1(9.8)(.05sin(10°)) 0.000015 = .05v^2 + .00851 At this point, my v^2 will equal a negative number, which makes no sense at all. I'm stuck >.< The problem is that the left side of the equation gets exponentially smaller while the right hand side... doesn't. Edit: Foolish calculator mistake. I hate how I find this out right after I posted it (I checked my work for 1/2 hr before posting). 1.2 N / cm = 120 N / m, not .012. I hit * instead of / on my calc.