Momentum and CollisionHard
Question
An object moving through air at a speed v. If the area of the object normal to the direction of velocity is A and assuming elastic collision with the air molecules, then the resistive force on the is proportional to - (assume that molecules striking the object were initially at rest)
Options
A.2Av
B.2Av2
C.2Av1/2
D.Can′t be determinate
Solution
Velocity of air molecule after collision = 2v. The number of air-molecules accelerated to a velocity 2v in time ᐃt is proportional to Av ᐃt. therefore F = 
∝ (Av ᐃt) 
⇒ F ∝ 2Av2
∝ (Av ᐃt) ⇒ F ∝ 2Av2Create a free account to view solution
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