Question
A 30 kg projectile moving horizontally with a velocity →v0=(120m/s)^i explodes into two fragments A and B of masses 12 kg and 18 kg, respectively. Taking point of explosion as origin and knowing that 3 s later the position of fragment A is (300, 24, –48) m, determine the position of fragment B at the same instant.
Answer: Option B
:
B
Initial coordinates of CM = (0, 0, 0)
x coordinates of CM after 3 s,
xCM=120×3=360m
y coordinates of CM after 3 s,
yCM=−12gt2=−45m
After 3 s,
(m1+m2)xCM=m1x1+m2x2
x2=30×360−12×30018=400m
Similarly, (m1+m2)yCM=m1y1+m2y2
−30×45=12×24+18×y2
y2=−91m
and in z coordinate, m1z1+m2z2=0⇒z2=32m
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:
B
Initial coordinates of CM = (0, 0, 0)
x coordinates of CM after 3 s,
xCM=120×3=360m
y coordinates of CM after 3 s,
yCM=−12gt2=−45m
After 3 s,
(m1+m2)xCM=m1x1+m2x2
x2=30×360−12×30018=400m
Similarly, (m1+m2)yCM=m1y1+m2y2
−30×45=12×24+18×y2
y2=−91m
and in z coordinate, m1z1+m2z2=0⇒z2=32m
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