For demonstrating the composition of a force and for determining the coefficients of friction between different materials. Heavy cast metal base 450x150x25mm, hinged to wood plane comprising two wood strips 480x60x20mm thick, 20mm apart, rigidly joined at ends by metal cross pieces: one strip with 51mm extension carrying a clamp for holding pulley at any angle with aluminium pulley, 44mm dia., on stem 150mm long. Linear scale fixed to edge of plane and vertical linear 0-45° angular scales screwed to metal base. The plane can be fixed at any angle with clamping wing nut.