question_answer

When a body falls in air, the resistance of air depends to a great extent on the shape of the body. 3 different shapes are given. Identify the combination of air resistances which truly represents the physical situation. (The cross sectional areas are the same).                 

A)  \[1<2<3\]                          

B)  \[2<3<1\]

C)  \[3<2<1\]          

D)  \[3<1<2\]

Correct Answer: C

Solution :

From the figure.                 \[{{T}_{1}}\cos {{30}^{o}}={{T}_{2}}\cos {{30}^{o}}\] \[\therefore \]  \[{{T}_{1}}={{T}_{2}}=T\] (Let) Again \[{{T}_{1}}\sin {{30}^{o}}+{{T}_{2}}\sin {{30}^{o}}=10\] \[2T\sin {{30}^{o}}=10\]                 \[2T.\frac{1}{2}=10\,\,\,\,\Rightarrow \,\,\,\,T=10N\] \[\therefore \] Tension m section DC and BF are 10 N and 10 N