because both gravity and drag are acting in the same direction. The acceleration is not constant, as the
velocity changes during the cannonball’s flight. The velocity decreases on the upward journey, so the
acceleration will also decrease in magnitude. Finally, the acceleration is only g when the velocity is
zero at the very top of the flight.2 . A —The horizontal velocity is constant, and there is no horizontal acceleration in the absence of air
resistance.
3 . B —Both balls start from rest and pick up speed at the same constant rate of g = 9.8 m/s^2 . The first
ball simply starts 1.0 s ahead of the second ball and will remain a constant 9.8 m/s ahead. Since the
first ball is always 9.8 m/s faster than the second, the distance between the balls will always increase
as they fall.
4 . C —The displacement of the object is given by the area of the graph. The positive area from 0 to 2 s
is 3 m. The negative area from 2 to 3 s is 1 m, which is not enough to return to the origin. The negative
area from 2 to 4 s is 4 m, which is too large. Therefore, the object will pass through the origin
between 3 and 4 s as it travels in the negative direction.