Give reasons for the following:
a. Knives and swords are supposed to have extremely thin blades.
b. Lorries and trucks carrying heavy loads have 8 tires instead of four, and the
tires are broader.
c. Camels can walk easily in desserts but humans cannot.
d. In a flight, the human ear pain during take-off and landing.
e. A suction cup does not stick on a rough surface.

Two loudspeakers, 5.5 m apart and facing each other, play identical sounds of the same frequency. you stand halfway between them, where there is a maximum of sound intensity. moving from this point toward one of the speakers, you encounter a minimum of sound intensity when you have moved 0.33 m . assume the speed of sound is 340 m/s.part a) what is the frequency of the sound? part b) if the frequency is then increased while you remain 0.21 m from the center, what is the first frequency for which that location will be a maximum of sound intensity? express your answer to two significant figures and include the appropriate units.