A grandfather's clock is calibrated at a temperature of 20 degrees celcius. The pendulum is a thin brass rod with a heavy mass attached to the end. on a hot day, when the temperature is 30 degrees celcius does the clock 'run' fast or slow? how much time does it gain or lose in a 24 hour period? i've tried re-arranging delta L = aL delta T so that i could find the length without the change or vice versa and a few other substitution arrangments but nothing seems to be working out for me. please help me with finding how to derive an equation to solve this!