21. Why are teeth examples of wedges?
A. They can cut objects.
B. They can lift objects with less force.
C. They can pull down objects with less force.
D. They have fulcrum, force arms and work arms.
22. Which of the following has a sharp edge?
A. knife B. seesaw
C. spoon
D. stairs
23. What simple machine help people to do their work easier and faster like lifting heavy object?
A. broom
C. pulley
D. spoon
24. Which does NOT describe a movable pulley?
A. It moves along with the rope or load.
B. The direction of the force does not change.
C. The wheel of this pulley is firmly attached to a fixed point.
D. It decreases the distance but increases the force needed to exert.
25. Which simple machine is described as an inclined plane wrapped around a shaft, creating
grooves?
A. lever
B. pulley
C. screw
D. wheel and axle
B. cup
26. What type of simple machine is found at the bottom of the light bulb?
A. inclined plane
C. screw
B. lever
D. wedge​