1.

A force vec(F)=5 hat(i)+2hat(j)-5hat(k) acts on a particle whose position vector is vec(r)=hat(i)-2hat(j)+hat(k). What is the torque about the origin ?

Answer»

`8 HAT(i) + 10 hat(j) + 12 hat(k)`
`8hat(i) + 10 hat(j) - 12 hat(k)`
`8hat(i) - 10 hat(j) - 8hat(k)`
`10 hat(i) - 10 hat(j) - hat(k)`

Solution :`VEC(TAU) = vec(r) xx vec(F) |(hat(i),hat(j), hat(k)),(1, -2,1),(5,2,-5)| = hat(i)(10-2) - hat(j)(-5-5) + hat(k)(2+10) = 8hat(i) +10 hat(j) + 12 hat(k)`


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