Question

If the upward direction is positive, which situation involves negative velocity and positive acceleration?

• A. An elevator moving upward at a constant speed
• B. An elevator speeding up as it moves downward
• C. An elevator speeding up as it moves upward
• D. An elevator slowing down as it moves downward

Answer 1

The correct option is D An elevator slowing down as it moves downward

As velocity is the rate of change of displacement, when the elevate is going down the displacement is decreasing thus the velocity is negative. But since the acceleration is positive, the rate of change of velocity is positive. So, the velocity is increasing but it is negative, its magnitude (speed) is going down with time.