1. The problem statement, all variables and given/known data So with pendulums in SHM, in my A level physics textbook (AQA Physics A), it shows a pendulum that has been displaced from equilibrium. It says that the restoring force is provided by the object's weight. Why isn't the restoring force provided by the tension in the string holding the pendulum ball up? It also says that mgsinθ is the restoring force, because it's the horizontal component of the object's weight, but why does the weight of the object have those components if it's acting straight downwards?