Question 11
FrictionA parachute attains a terminal velocity when
- A.its density is equal to the density of air
- B.the viscous force of the air and the upthrust completely counteract its weight
- C.it expands as a result of reduced external pressure
- D.the viscous force of the air is equal to the sum of the weight and upthrust
Show the answer and explanation
Answer: B (the viscous force of the air and the upthrust completely counteract its weight)
Explanation
At terminal velocity there is no resultant force: the upward forces (air resistance and upthrust) exactly balance the weight, so the speed stays constant.