Four Identical Blocks Are Moving on a Surface for Which

Multiple Choice

Four identical blocks are moving on a surface for which the coefficient of kinetic friction between each block and the surface is µ_k. The velocity of each block is indicated by the vector on the block. For which block is the force of friction between the surface and the block greatest?

A) 1
B) 2
C) 3
D) 4
E) The force of friction is the same for all blocks.