How much time is needed for a boy on roller skates to slow down from 17.4

m/s to 9.11 m/s if he covers 45.0 m?

Step-by-step explanation:

v²-u²=2as

9.11²-17.4²=2a*45

a = - (17.4²-9.11²) / 90 = - (302.76-82.9921) / 90=-219.7679/90 m/s²

v=u+at

9.11=17.4-219.7679/90 t

9.11-17.4=-219.7679/90t

-8.29*90=-219.7679t

t=-746.1/-219.7679≈3.395 s