Drag and air resistance Knowledge-Based Practice

Questions

1. 1.

   A skydiver is falling vertically downward at terminal speed when their parachute opens, causing the upward drag force to become greater than the downward gravitational force. Immediately after the parachute deploys, which statement correctly describes the skydiver's motion and acceleration?

   • A) The skydiver continues moving downward while experiencing an upward acceleration that reduces their downward speed.
   • B) The skydiver begins moving upward because the upward net force immediately reverses the direction of motion.
   • C) The skydiver momentarily comes to a complete stop before continuing downward at a lower constant speed.
   • D) The skydiver continues moving downward while experiencing a downward acceleration of reduced magnitude.
2. 2.

   Two solid spheres of identical radius and surface finish, one made of aluminum and the other of lead, fall vertically through air until each achieves terminal speed. How does the terminal speed of the heavier lead sphere compare to that of the aluminum sphere, and why?

   • A) The lead sphere has a smaller terminal speed because its greater mass causes it to encounter higher air resistance at any given speed.
   • B) Both spheres reach the same terminal speed because terminal speed is determined solely by cross-sectional area and drag coefficient.
   • C) The lead sphere has a smaller terminal speed because denser objects reach mechanical equilibrium more rapidly.
   • D) The lead sphere has a greater terminal speed because a larger drag force is required to balance its greater weight.
3. 3.

   A projectile is launched vertically upward through air where aerodynamic drag cannot be neglected. While the projectile is moving upward, how does the magnitude and direction of its acceleration compare to the acceleration due to gravity, $g$?

   • A) Greater than $g$ and directed downward
   • B) Less than $g$ and directed downward
   • C) Equal to $g$ and directed downward
   • D) Greater than $g$ and directed upward
4. 4.

   An object is dropped from a high altitude and falls vertically through the air until it reaches terminal velocity. Which statement correctly describes the forces and motion of the object at the moment terminal velocity is achieved?

   • A) The drag force is zero, and the object accelerates at the local acceleration due to gravity.
   • B) The upward drag force exceeds the downward gravitational force, causing the object to decelerate.
   • C) The upward drag force balances the downward gravitational force, resulting in zero acceleration and constant velocity.
   • D) The drag force drops to zero because the object is no longer accelerating.

Answers and step-by-step solutions appear after you finish the test.