KCET2014PhysicsOscillations
A force ( F =5 i +2 j -5 k ) acts on a particle whose position vector is ( r = i -2 j + k ). What is the torque about the origin ?
Options
- A( 8 i +10 j +12 k )
- B( 8 i +10 j -12 k )
- C( 8 i -10 j -8 k )
- D( 10 i -10 j - k )
Correct answer
A. ( 8 i +10 j +12 k )
Step-by-step solution
Given ( F =5 i +2 j -5 k ; r = i -2 j + k ) We know torque [ = r F = | array ccc i & j & k 1 & -2 & 1 5 & 2 & -5 array | ] Therefore, [ array l = i (10-2)- j (-5-5)+ k (2+10) =8 i +10 j +12 k array ] Thus, torque about origin is ( 8 i +10 j +12 k )