Force f = − + ( 8.00 n i 6.00 n j ) ( ) acts on a particle with position vector r = + (3.00 m i 4.00 m j ) ( ) .

what are

(a) the torque on the particle about the origin, in unit-vector notation
(b) the angle between the directions of r and f ?

Explanation:

Given that,

Force,

Position of the particle,

(a) The toque on a particle about the origin is given by :

Taking the cross product of above two vectors, we get the value of torque as :

(b) Let is the angle between r and F. The angle between two vectors is given by :

see earlier answer

not moving. pos accel,