Question

Michael Phelps needs to swim at an average speed of 2.00 m/s in order to set a new world record in the 200 m freestyle. If he swims the first 100 meters at an average speed of 1.80 m/s how fast must he swim the second 100 meters in order to break the record?

Answer 1

Answer:

Explanation:

Given

average speed of Phelps $v_{avg}=2\ m/s$

total distance $d=200\ m$

he swims first 100 m at an average speed if $1.8 m/s$

so time taken is $t_1=\frac{100}{1.8}=55.55\ s$

suppose $t_2$ is the time taken to swim remaining half

average velocity is $v_{avg}=\frac{displacement}{total\ time}$

$v_{avg}=\frac{100+100}{55.55+t_2}$

$t_2+55.55=\frac{200}{2}=100$

$t_2=44.45\ s$

so velocity in the second half is

$v_2=\frac{100}{45.45}$

$v_2=2.19\approx 2.2\ m/s$