dane: h = 3m l = 20m g = 10m/s2 szukane: v = ? t = ? Z II zasady dynamiki: F = m *a m*g*sin(alfa) = m*a /:m a = g*sin(alfa) sin(alfa) = h/l = 3/20 a = 10m/s2 *3/20 a = 3/2 m/s2 = 1,5 m/s2 Liczę czas "t" ze wzoru na drogę w ruchu jednostajnie przyspieszonym: s = at^2/2 I*2 at^2 = 2s /:a t^2 = 2s/a t = V(2s/a) = V(2*20m:3/2m/s2) = V(80/3) [s] = 4V(5/3) s = 4 *1,3 [s] t = 5,2 s v = a*t = 1,5m/s2 * 4V(5/3)s = 6 *1,3 m/s v = 7,8 m/s Odpowiedź: Chłopiec uzyska predkość 7,8m/s w czasie 5,2s.
h = 3m l = 20m g = 10m/s2 v = ? t = ? F = m *a m*g*sin(alfa) = m*a /:m a = g*sin(alfa) sin(alfa) = h/l = 3/20 a = 10m/s2 *3/20 a = 3/2 m/s2 = 1,5 m/s2 s = at^2/2 I*2 at^2 = 2s /:a t^2 = 2s/a t = V(2s/a) = V(2*20m:3/2m/s2) = V(80/3) [s] = 4V(5/3) s = 4 *1,3 [s] t = 5,2 s v = a*t = 1,5m/s2 * 4V(5/3)s = 6 *1,3 m/s v = 7,8 m/s- WYNIK ; )
