Ared car and a blue car can move along the same straight one-lane road. both cars can move only at one speed when they move (e. g., 60 mph). the driver of the red car sounds his horn. in which one of the following situations does the driver of the blue car hear the highest horn frequency? a. both cars are moving at the same speed, and they are moving apart. b. both cars are moving in the same direction at the same speed. c. both cars are moving at the same speed, and they are moving toward each other. d. the red car is moving toward the blue car, which is stationary. e. the blue car is moving toward the red car, which is stationary.

c

Explanation:

When both cars move towards each other with same speed , apparent frequency will be highest

this can also be explained by Doppler frequency Formula

where

as denominator is smaller than Numerator therefore apparent frequency will be greater

it is given that trillions of microbes make up to 1% to 3% of the body mass.

let's take average of this percentage: 2%

consider the average mass of the human body as 70 kg.

then, trillions of microbes would have mass  

therefore, 100 trillion micro-organisms would weigh:

this is an approximate value and could change depending on the mass of the human body and percentage of the microbes present in it.

average mass per microorganism =