B
bluestar_0410


Mot vat dao dong dieu hoa theo pt: x=6cos(5.pi.t - pi/4) cm. Tinh tu luc bat dau khao sat dao dong, lan thu hai vat co van tôc v2=-15pi cm/s vao thoi diem:
a, 13/60s
b, 39/180s
c, 5/60s
d, 7/12s
a, 13/60s
b, 39/180s
c, 5/60s
d, 7/12s