physics
posted by Lindsay .
In order to change the angular momentum of an object, it is necessary to apply
a. a net force to the object.
b. a net torque to the object.
c. a centripetal acceleration to the object.
d. both a net force and a net torque to the object.
We have three vectors, labeled A, B, and C. A points due west, B points due north, and C points due east. We donâ€™t know their relative magnitudes. We find the cross product of each of these vectors with a vector which points due south (D). Rank the three cross products ( ) from smallest to largest in terms of their vertical component, taking the sign of the component into account.
g. You cannot tell with the given information

To change angular momentum requires a moment(torque)

LOL, yes you can tell
first B X D
the angle between B and D is 180, and the sine of 180 is zero
therefore B X D = 0
that was easy
Now A X D
rotation from A to D is + 90 degrees, so A X D is UP, positive
But C X D
rotation from C to D is negative 90 degrees, cross product down
C X D is DOWN, negative
Thus
in order
CXD negative
BXD zero
AXD positive