You pull a solid nickel ball with a density of 8.91 g/cm3 and a radius of 1.40 cm upward through a fluid at a constant speed of 9.00 cm/s. The fluid exerts a drag force that is directly proportional to speed, and the proportionality constant is 0.950 kg/s. What is the magnitude of the force (in N) you exert on the ball? (You may ignore the buoyant force.)

Explanation:

The constant speed means that ball is not experimenting acceleration. This elements is modelled by using the following equation of equilibrium:

Now, the exerted force is:

The volume of a sphere is:

Lastly, the force is calculated:

acceleration = (change in speed) / (time for the change)

change in speed = (20-120)= -100 m/s.

1.5 min = 90 sec

acceleration = -100/90 = -1.11 m/s^2.

we don't care about the 150kg or the 2,500 meters. they don't make any difference.

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