Answer to Question #9835 in Mechanics | Relativity for Helen Moody

Question

Modern day draw bridges are also known as bascule bridges. These can have one or two sides (one is called a leaf) that are drawn up from each end of the bridge so that boats can pass through water channels. In some designs, each side of the bascule bridge is held in place by a counter-weight located in a pier placed on the river bank. Imagine one side of a two-leaf bascule bridge. The length of one leaf of the bascule bridge is 25m (from pivot point on the pier to the edge of the leaf that meets the opposite leaf in the middle of the river). The mass of the leaf is 10 000 kg. If the counter weight is located one metre on the other side of the pivot point. (Hint: The mass of the leaf should be taken from the centre of the leaf and we assume the leaf is at equilibrium in the down position)