The tail board of a lorry is 1.5 m long and 0.75 m high. It is hinged along the bottom edge to the floor of the lorry. Chains are attached to the top corners of the board and to the sides of the lorry so that when the board is in a horizontal position the chains are parallel and inclined at 45° to the horizontal. A tension spring is inserted in each chain so as to reduce the shock and these are adjusted to prevent the board from dropping below the horizontal. Each spring exerts a force of 60 N/mm of extension. Find the greatest force in each spring and the resultant force at the hinges when the board falls freely from the vertical position. Assume that the tail board is a uniform body of mass 30 kg.

The tail board of a lorry is 1.5 m long and 0.75 m high. It is hinged along the bottom edge to the floor of the lorry. Chains are attached to the top corners of the board and to the sides of the lorry so that when the board is in a horizontal position the chains are parallel and inclined at 45° to the horizontal. A tension spring is inserted in each chain so as to reduce the shock and these are adjusted to prevent the board from dropping below the horizontal. Each spring exerts a force of 60 N/mm of extension. Find the greatest force in each spring and the resultant force at the hinges when the board falls freely from the vertical position. Assume that the tail board is a uniform body of mass 30 kg.