1. The problem statement, all variables and given/known data The position of a 2.75x10^5 N training helicopter under test is given by...? vector r = (0.020m/s^3)t^3ihat+(2.2 m/s)tjhat-(0.060m/s^2)t^2 khat Find the net force on the helicopter at t=5.0s Express your answer in terms of ihat, jhat , and khat . Express your coefficient using two significant figures. 2. Relevant equations 3. The attempt at a solution I dont understand why me must take the second derivative, already solved it just want some clarification on to why we get the second derivative. Thank you!