A boy inline-skates over smooth pavement at a velocity of 6.2 m/s south. The path turns to rough asphalt, so the boy slows down with an acceleration of 1.3 m/s2 north. If his velocity on the asphalt is now 4.3 m/s south, how long did it take him to slow down

Explanation:

The time taken for decreasing the speed can be calculated by the relation

v = u - a  t

here v is the final velocity

u is the initial velocity and a is the acceleration

Thus 4.3 = 6.2 - 1.3 x t

or t =  1.53 s  

grav force prop 1/r squared 2r all squared is 4rsquared 1/4rsquared quartered