A ball bearing is gently released from rest and allowed to fall through a viscous fluid. Which of the following statements about the motion is correct?
A ball bearing is gently released from rest and allowed to fall through a viscous fluid. Which of the following statements about the motion is correct?
Answer Details
As the ball bearing falls through the viscous fluid, the fluid exerts a resistive force against the motion of the ball bearing. This resistive force opposes the motion of the ball bearing and increases with its speed until it becomes equal to the weight of the ball bearing. At this point, the ball bearing stops accelerating and reaches a constant speed called the terminal velocity. Therefore, the correct statement about the motion is: when terminal velocity is attained, the acceleration of the ball bearing becomes zero.
Option (a) is incorrect because the acceleration of the ball bearing decreases as it approaches the terminal velocity. Option (c) is incorrect because the velocity of the ball bearing increases initially, but as it approaches terminal velocity, the increase in velocity slows down until it becomes constant. Option (d) is incorrect because there is a resultant force acting on the ball bearing before it attains terminal velocity, which is the difference between the weight of the ball bearing and the resistive force of the fluid.