1. The problem statement, all variables and given/known data "Two people are holding a plank of wood at either end, with a mass located at the halfway point between them, they both walk backwards extending their arms, the mass still being halfway between them. The plank becomes harder to support, why is this?" 2. Relevant equations Maybe the idea of moments? 3. The attempt at a solution If it involves the use of moments do I deem the people are acting as pivots? As I haven't really given a "solution" could you perhaps point me in the right direction, so I can come to the answer? Thanks.