Steve does 80 J of work to a rope threaded through a pulley and attached to a crate of anvils. The tension of the rope is 10 N and the crate rises 4 m while Steve pulls. What is the efficiency of the pulley? [Hint: how much work was done on the crate?] a) (A) 0.07 or 7 %
b) (B) 0.2 or 20 %
c) (C) 0.5 or 50 %
d) (D) 1 or 100 %

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.