15. The force shown in the
force vs. time diagram in
Figure P6.15 acts on a 1.5-kg
object. Find (a) the impulse
of the force, (b) the final
velocity of the object if it is
initially at rest, and (c) the
final velocity of the object
if it is initially moving along
the x-axis with a velocity of
-2.0 m/s.