Physics

Average Speed and Velocity

total displacement total distance
Average velocity= Average speed=
timeinterval totaltime


∆d d total
v av = sav =
∆t t total


d 2−d 1 d 1 +d 2 +…+d n
v av = sav =
t 2−t 1 t 1+ t 2 +…+t n




Sample problems:

1. A track and field runner warming up for a game runs along a track. He runs 50 meters North
and then runs 30 meters back toward the starting point before stopping to talk to the coach. If
he runs 20 seconds, determine the following:

a. Runner’s average velocity
Given:

d 2 = 20m North d1 = 0 t 2 = 20 seconds t1 = 0


Computation:

20−0 = 20 m
v av = =1 North
20−0 20 s


Answer:

The runner’s average velocity is 1.0 m/s going in the positive direction or expressed as 1.0 m/s
North.

b. Runner’s average speed
Given:

d 2 = + 50m d 1 = -30m t 2 = 20 seconds t1 = 0


Computation:

50+30 80
v av = = =4 m/s
20+0 20


Answer:

The runner’s average is 4 m/s.