### Video Transcript

An object is moving northward at a
speed of two meters per second. If the object decreases its
velocity in the northward direction by three meters per second, which of the
following correctly describes the direction in which the object is now moving? (A) The object is moving
northward. (B) The object is not moving. (C) The object is moving
southward.

When an object decreases its
velocity in the direction that the object is traveling in, one of these three things
must happen. The object continues moving in the
same direction but at a decreased speed. Two, the object could come to
rest. Three, the object reverses the
direction in which it moves. Letβs say that the object in this
example has an initial velocity that weβll call π£ sub π. We can call the change in the
objectβs speed βπ£ written like this. Lastly, letβs say that the final
velocity of the object is π£ sub π. For any values of these variables,
it is true that π£ sub π equals π£ sub π plus βπ£.

Recall that the change of velocity
of the object is in the opposite direction to the initial velocity of the
object. If we define π£ sub π as positive,
βπ£ must be negative as it is in the opposite direction to π£ sub π. Since π£ sub π is positive and βπ£
is negative, we can say that if the magnitude of π£ sub π is greater than the
magnitude of βπ£, π£ sub π is greater than zero. This means that the object
continues moving in the same direction but at a decreased speed. Itβs also possible that the
magnitude of π£ sub π equals the magnitude of βπ£, in which case π£ sub π equals
zero, telling us the object has stopped moving. And lastly, if the magnitude of π£
sub π is less than that of βπ£, π£ sub π is negative, which means the object
reverses direction.

In this question, the initial
velocity has a magnitude of two meters per second and the decrease in velocity has a
magnitude of three meters per second. So that means the magnitude of π£
sub π is less than the magnitude of βπ£. Therefore, π£ sub π is less than
zero, and the object reverses the direction in which it moves. The object is initially traveling
northward. And so when it reverses direction,
it must start traveling southward. Therefore, the correct answer is
(C). The object is moving southward.