Question

26.Un tren se deplaseaza cu viteza constanta de 90 km/h trecand printr un punct A aflat la 500 m de statia S.Cu 20 s inainte de statie, mecanicul actioneaza frana si trenul se opreste in statie.VA ROG!DAU COROANA!PROBLEMA ACEASTA M AR AJUTA FOARTE MULT LA SCOALA!!!!!!​

Answer 1

Răspuns:

a)

a = (vf - vi)/t

vf = 0 m/s

vi = 90km/h = 90000m/3600s = 25 m/s

t = 20 s

a = (0m/s - 25m/s)/20s = (- 25m/s)/(20s) = - 1, 25 m/s²

b)

vm = (vi + vf)/2 = (25m/s + 0m/s)/2 = 12, 5m/s = 45km/h

c)

A |______|_______| S

                X

v(XS) = d(XS)/t => d(XS) = v(XS)×t

v(XS) = vm = 12,5 m/s

t = 20 s

v(XS) = 12,5m/s×20s = 250 m

d)

t(AX) = d(AX)/v = 250m/(25m/s) = 10 s

t(AS) = t9AX) + t(XS) = 10s + 20s = 30s