Question

A 4.01kg wood block is pressed against a vertical wood wall by a force applied at angle ϕ=33.0° to the horizontal. Knight Problem0552 Image If the block is initially at rest, and μs=0.357, what force would you need to apply to begin moving the box up the wall?

Answer 1

The upward component of the applied force should be equal in magnitude to the sum of the block's weight and the force of static friction directed down. F sin(33) = F cos(33) ÎĽs + mg F sin(33) - F cos(33) ÎĽs = mg F (sin(33) - cos(33) ÎĽs) = mg F = mg / (sin(33) - cos(33) ÎĽs) F = (4.01 kg) (9.80 m/s^2) / (sin(33) - cos(33) (0.357)) F = 160 N We would need to apply a force of 160 N