Imagine you are riding a bike the wrong way on a moving sidewalk in an airport. your bike's speedometer says you are moving 20 mph, and the sidewalk moves at 5 mph. if there is a guy at the end of the sidewalk with a radar gun, what will his gun read if the direction of the sidewalk is taken to be positive? 25 mph 15 mph -15 mph -25 mph

Velocity= 25mph

Explanation:

The relative velocity between two bodies is the value of the velocity of one of them as measured by an observer located in the other.

In this case, the speed of the bicycle and the speed of the sidewalk are in the opposite direction, so the relative speed of the bicycle with respect to an observer who is on the sidewalk in motion will be the sum between the speed of the 25 mph bike plus sidewalk speed (with the observer) 5 mph.

Thus the relative speed of the bicycle is obtained from the observer, which measures the radar gun. This will be:

Velocity= v= 20mph + 5mph= 25mph

hi there!

out of the two, (b) precision would be more reasonable.   however, both a and b could be pretty reasonable.

-awesomerepublic   : )

that tool is called an altimeter which measures your altitude which can be used to tell which atmosphere you are currently in, including the stratosphere.

hope this ! : )