Friction Apparatus (812) This set includes a friction block and a friction board, both made of high quality, smoothly finished pine wood. The friction block has a hook for a spring scale and three compartments for additional weights. It can be placed face-up or sideways. Students can vary the weight or area of contact to see their impact on the friction force. Comes with 3-50g weights and a 100g spring scale. Board is 20" x 2" and the block is 4" x 1.5" x 1". Qty :