Question

Army is standing still on the ground; Bill is riding his bicycle at 5 m/s eastward: and Carlos is driving his car at 15 m/s westward. How fast does Bill see Carlos moving and in what direction?

a. 10 mis eastward
b. 5 m/s eastward
c. 15 m/s westward
d. 20 m/s westward
e. 10 m/s westward

Answer 1

Step-by-step explanation:

Given that,

Bill is riding his bicycle at 5 m/s eastward: and Carlos is driving his car at 15 m/s westward.

Taking eastward as positive direction, we have:

`v_B=+5\ m/s`is the velocity of Bill with respect to Amy (which is stationary)

`v_c=15\ m/s` is the velocity of Carlos with respect to Amy.

Bill is moving 5 m/s eastward compared to Amy at rest, so the velocity of Bill's reference frame is

`v_B=+5\ m/s`

Therefore, Carlos velocity in Bill's reference frame will be

`v_c'=-15\ m/s-(+5\ m/s)\\\\=-20\ m/s`

So, the magnitude is 20 m/s and the direction is westward (negative sign).