Question

A football quarterback runs 13 m straight down the playing field in 2.8 s. He is then hit and pushed 3.1 m straight backward in 1.4 s. He breaks the tackle and runs straight forward another 21 m in 5 s. Calculate his average velocity for the entire motion, in SI units, and express the numeral of your answer.

Answer 1

`v_(avg) = 3.36 m/s`

S.I unit is m/s

numeral value is 3.36

Given:

displacement, d = 13 m

displacement, d' = - 3.1 m

displacement, d'' = 21 m

time, t = 2.8 s

time, t' = 1.4 s

time, t'' = 5 s

Solution:

The average velocity of a body is given by:

`v_(avg) = (Total distance traveled or total displacement)/(Total time taken)`

`v_(avg) = (d + d'+ d'')/(t +t'+t'')`

`v_(avg) = (13 - 3.1 + 21)/(2.8 + 1.4 + 5) = 3.36 m/s`

where

Total distance traveled = |d| + |d'| + |d''| = 13 + 3.1 + 21 = 37.1 m

Total displacement = d + d' + d'' = 13 - 3.1 + 21 = 30.9 m