To a stationary observer, a bus moves north with a speed of 10 m/s. A man inside walks toward the back of the bus with a speed of 0.4 m/s relative to the bus. What is the velocity of the man according to a stationary observer?

A. 0.4 m/s north
B. 10.4 m/s north
C. 10 m/s north
D. 9.6 m/s north

Question

To a stationary observer, a bus moves north with a speed of 10 m/s. A man inside walks toward the back of the bus with a speed of 0.4 m/s relative to the bus. What is the velocity of the man according to a stationary observer?

 		A.	0.4 m/s north
 		B.	10.4 m/s north
 		C.	10 m/s north
 		D.	9.6 m/s north

anonymous · Answer

Do you have an educated guess as to what the answer might be? 

Think of it like this: You are observing to cars that are facing away from each other. When both move away at 10m/s, to you, how fast are they moving away from each other?