Formula: s_n = u + (a/2)(2n - 1)

Key points:

1. s_n is displacement in the nth second, NOT distance
2. s_n can be negative (means body moved backward in that second)
3. When s_n = 0, the body has zero displacement in that second (momentary reversal)
4. s_n = 0 when n = (1/2) - u/a + 1/2 = (1 - 2u/a + 1)/2... Better: set u + a(2n-1)/2 = 0

Finding when body reverses: Body reverses when v = 0. t_reverse = -u/a (must be positive, so u and a must have opposite signs)

Distance calculation: Split motion at the reversal point.

• Distance from t=0 to t_reverse: |s_1|
• Distance from t_reverse to t_total: |s_2|
• Total distance = |s_1| + |s_2|