A particle is acted upon by constant forces 4^i+^j−3^k and 3^i+^j−^k which displace it from a point ^i+2^j+3^k to the point 5^i+4^j+^k. The work done is standard units by the forces is given by:
A
40
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B
30
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C
25
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D
15
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Solution
The correct option is B40 Total force =(4^i+^j−3^k)+(3^i+^j−^k)=7^i+2^j−4^k The particle is displaced from A(^i+2^j+3^k) to B(5^i+4^j+^k) Therefore displacement AB=(5^i+4^j+^k)−(^i+2^j+3^k)=4^i+2^j−2^k Work done =F.AB=(7^i+2^j−4^k).(4^i+2^j−2^k)=28+4+8=40