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B Forces Question

  1. Jun 27, 2017 #1
    Hi! I'm thinking how would the velocity of a sphere change if it falls from rest in a tall beaker full of oil. I know that the direction of acceleration is upwards, and the acceleration should be decreasing at a decreasing rate. But how would the velocity change if the velocity is initially zero and falling downwards, meaning the acceleration has to slow it down. How does it slow down when the velocity is zero? And how can it be for the ball not to have velocity when it falls? Thanks.
  2. jcsd
  3. Jun 27, 2017 #2
    The force of gravity on the sphere will be a constant. The force against the fluid will be a function of its velocity through the fluid.
    At zero velocity, the force from the fluid will be zero and only gravity will be acting on it. These two forces would balance out at a "terminal velocity". So, as the sphere approaches that velocity, the acceleration will approach zero.
  4. Jun 27, 2017 #3
    Ok. Thank you very much!
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