the position of a person on a scateboard os givin by
s= t^2 - 8t + 12
where s is measured in meters and t, in seconds
When is the person at rest?
• when v=o
When is the person moving in a positive direction?
s= t^2 - 8t + 12
= ( t - 6) ( t - 2)
(t - 6)
________0_______2______6_______
(t - 6)............neg.......neg........pos
(t - 2)............neg.......pos.........pos
s(t)................pos.........neg.......pos
so it is at a pos direction at o<t<2 and t>6, but the book said t>4
s= t^2 - 8t + 12
where s is measured in meters and t, in seconds
When is the person at rest?
• when v=o
When is the person moving in a positive direction?
s= t^2 - 8t + 12
= ( t - 6) ( t - 2)
(t - 6)
________0_______2______6_______
(t - 6)............neg.......neg........pos
(t - 2)............neg.......pos.........pos
s(t)................pos.........neg.......pos
so it is at a pos direction at o<t<2 and t>6, but the book said t>4
