Questions: Air Resistance, Drag Forces, and Terminal Velocity

Question 1

A skydiver falls at constant terminal velocity. Which statement is correct?

• A. No forces act on the skydiver
• B. Drag is larger than the skydiver's weight
• C. Drag equals the skydiver's weight, so the net force is zero
• D. Gravity has switched off

Answer: (C)

Constant velocity means zero acceleration, so the net force is zero. Drag balances weight.

Question 2

An object falls with quadratic drag F = cv². A second object has the same shape and size but four times the mass. How does its terminal speed compare?

• A. The same
• B. Twice as large
• C. Four times as large
• D. Sixteen times as large

Answer: (B)

At terminal speed mg = cv², so v_t = √(mg/c). Four times the mass gives √4 = 2 times the terminal speed.

Question 3

With linear drag, a falling object reaches exactly its terminal speed after one time constant τ = m/b.

• T. True
• F. False

Answer: False

The speed is v(t) = v_t(1 − e^(−t/τ)). After one time constant it has reached about 63% of v_t. It approaches v_t only as time goes on without limit.

Question 4

A 0.010 kg object experiences linear drag with b = 0.0020 kg/s. Using g = 9.8 m/s², what is its terminal speed?

Model answer: 49 m/s

Setting mg = bv_t gives v_t = mg/b = (0.010 × 9.8)/0.0020 = 49 m/s.