Hey everyone. I have 2 relatively basic questions about horizontal springs. I feel like the questions are actually very simple (it's just highschool physics) but I think I'm approaching it the wrong way. Any help would be greatly appreciated. 1. I'm supposed to find the spring constant when a 5.5kg mass is vibrating at the end of a horizontal spring. It reaches a maximum speed of 7.2m/s and has a maximum displacement of 0.23m. Ignore friction. 2. I'm supposed to find the acceleration of a 4.97kg mass when the displacement of the mass is 2.56m. It oscillating on the end of a horizontal spring with a frequency of 0.467s to the left. 1. I thought I should first find the acceleration, then force (F=ma) and then solve for the spring constant (k=-F/x). To find the acceleration, I used a=V^2/2d. However, that gave me almost 113m/s. Surely that isn't correct... I feel like I should be using equations for energy somewhere, but I'm not sure which ones. 2. I tried a similar thing here, using a=2d/t^2. I assumed that I should divide time by 2, because that's the time for a complete oscillation, and I'm only calculating half (2.56m and back to equilibrium). However, this gives me an acceleration of almost 94 m/s^2, which also doesn't feel right. Thanks in advance!