Plastered block on inclined plank · Physics Brawl 2015 #FoL.2
Physics · mechanics
Problem
Kuba is boasting that he can lay a perfectly smooth cuboid on an inclined plank in such way that the cuboid won't slip down. The plank is inclined at an angle α=20° to the horizontal plane. Find out what Kuba's acceleration has to be when he holds the plank, so that the cuboid would remain at rest (with respect to the plank).