A cargo ship will unload big boxes at the pier. Which of these machines will the men use?
A. block and tacked pulley
B. fixed pulley
C. lever
D. screw
7. Which of the following makes use of the principle of the screw?
A. bulb
B. can opener
C. knife
D. scissors
8. Which statement is true about wedges?
A. If the wedge is thinner, no effort is needed at all.
B. If the wedge is thinner, the effort needed is more than the resistance.
C. If the wedge is thinner, the effort needed is equal to the resistance.
D. If the wedge is thinner, the effort needed is less than the resistance.​