
The velocity at time
is

Take two vectors that point in the positive
and positive
directions, such as
and
. The dot products of the velocity vector with
and
are

and

We want the angles between these vectors to be 45º, for which we have
. So



When
, the velocity vector is equal to the zero vector, which technically has no direction/doesn't make an angle with any other vector. So the only time this happens is for

Answer:
B. 36 lb
Explanation:
m = 160/9.8 = 16.3 kg
16.3 kg ( 2.205 lb/kg) = 36 lb