its density is equal to the density of air
the viscous force of the air and the upthrust completely counteract its weight
it expands as a result of reduced external pressure
the viscous force of the air is equal to the sum of the weight and upthrust
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The correct answer is B. the viscous force of the air and the upthrust completely counteract its weight.
Terminal velocity is reached when the force of gravity (weight) pulling the parachute down is balanced by the force of air resistance (viscous force) pushing it up, and the upthrust (buoyancy force) counteracts the weight. At this point, the parachute no longer accelerates, and its velocity remains constant.
Here's a breakdown of the forces:
- Weight (W) = mg (downward)
- Viscous force (Fv) = -kv (upward)
- Upthrust (Bu) = ρVg (upward)
At terminal velocity, the net force is zero:
W + Fv + Bu = 0
mg + (-kv) + ρVg = 0
The parachute reaches terminal velocity when the viscous force and upthrust balance its weight.
