[SOLVED] Simple pendulum: does the period change in a horizontally accelerating frame 1. The problem statement, all variables and given/known data Simple pendulum which is 5.0m long. What is its period when it is in a truck accelerating horizontally at 5.0m/s/s? 2. Relevant equations w = sqrt(g/d) w = 2pi/T 3. The attempt at a solution I want to say it is simply 2pi/T = sqrt(9.81/5.0m), but I am unsure if that equation applies in a horizontally accelerating frame of reference. Any advice appreciated, thanks!