8. The coefficient of static friction between a concrete block and a surface is 0.8. The block weighs 20 lbf. If a horizontal force of 15 lbf is applied to the block, would the block move?
And if not, what is the magnitude of friction force? What should be the magnitude of the
horizontal force to set the block in motion?

Sawyer is studying diffraction. he draws a diagram of a plane wave to show how light waves travel. which best describes sawyer’s error? the wave fronts should be perpendicular to the direction in which the waves move. the arrow showing the direction of movement of the waves should be pointing to the left. the arrow showing the direction of movement of the waves should be pointing downward. the wave fronts should be both parallel and perpendicular to the direction in which the waves move.