Three bodies of masses 1kg, 3kg and 4kg have position vectors (^i+2^j+^k), (−3^i−2^j+^k) and (4^i) respectively . The centre of mass of this system has position vector
A
(2^i+^j−^k)2
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B
(2^i+^j+^k)2
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C
(2^i−^j−^k)2
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D
(2^i−^j+^k)2
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Solution
The correct option is D(2^i−^j+^k)2
Given, m1=1kg,x1=^i+2^j+^k m2=3kg,x2=−3^i−2^j+^k m2=4kg,x3=4^i →rCOM=∑ni=1miximi=m1x1+m2x2+m3x3m1+m2+m3 =1(^i+2^j+^k)+3(−3^i−2^j+^k)+4(4^i)1+3+4 =8^i−4^j+4^k8=(2^i−^j+^k)2