Question

MEDAL GIVEN TO BEST ANSWER.

A man walks 30 m to the west, then 5 m to the east in 45 seconds.

a. What is his displacement?

b. What was his total distance walked?

c. What is his average velocity?

d. What is his average speed?

Answer 1

A. The displacement is simply the change in distance with respect to a given point. In other words, the displacement is from start to finish. Since the man walks 30 m [w] and then turns 180 degrees and walks the opposite way back 5 m [E]. Then the displacement is simply 25 m [W]. Subtract 30 m [W] by 5 m [E] and you get 25 m [W].

B. This is simple. All you do is add the distance traveled up to get your total distance. So 25 m [W] + 5 m[E] = 30 m. The difference between displacement and distance is that displacement has a fixed reference point where you have to start. (displacement is a vector quantity). As for distance, distance does not have a reference point or starting point and so distance is a scalar quantity.

C. The formula for avg velocity is displacement/time. We have the displacement from previous calculations which is 25 m [W] and the total time travelled which is 45 seconds. Therefore, to get the average velocity, divide the displacement by the time. 25 m [W]/45 s = 0.55 m/s [w]. You have to indicate the DIRECTION because velocity is a vector quantity. A vector quantity means it has a magnitude and direction.


D. Last question. Okay, D is the same answer as for C. However, this time you want the speed. Speed is a scalar quantity and so it has only a magnitude and NO DIRECTION. Therefore, the answer is just 0.55 m/s.



DONE.