**1. The problem statement, all variables and given/known data**

A block slides upward on a rough, vertical wall at constant velocity when a force F of 60 N acts on it at an angle Ɵ = 60ᵒ to the horizontal. The mass of the block is 3.0 kg. See picture below.

a) Using Newtons laws, find the normal force on the block.

b) Determine the force of kinetic friction on the block.

**2. The attempt at a solution**

a) N = mg – F_{y} = (3.0)(9.8) – 60sin60° = -23

b) Fcos60° – μN = 0

60cos60° + 23μ = 0

μ = -1.3

a negative coefficient?

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