JEE Main20205 Sep 2020Morning ShiftPhysicsRotational MotionActual
A force F → = ( i ^ + 2 j ^ + 3 k ^ )   N acts at a point ( 4 i ^ + 3 j ^ - k ^ )   m . Then the magnitude of torque about the point ( i ^ + 2 j ^ + k ^ )   m will be x   N - m . The value of x is..........
Correct answer
0
Step-by-step solution
r → = 4 - 1 i ^ + 3 - 2 j ^ + - 1 - 1 k ^ = 3 i ^ + j ^ - 2 k ^ τ = r → × F → = i ^ j k ^ 3 1 - 2 1 2 3 = i ^ 7 - j ^ 11 + k ^ 5 = 7 i ^ - 11 j ^ + 5 k ^ = 49 + 121 + 25 = 195