Drag and Lift

Q. Drag force is a function of______.

1. Projeced area of the body
2. Mass density of the fluid
3. Velocity of the body
4. All of the above

Q. The overall drag coefficient of an aircraft of weight W and wing area S is given by

$C_D=a+b{C}_L^2$

Where 'a' and 'b' are constants. The maximum drag in horizontal flight will be

1. $W\sqrt{ab}$
2. $2W\sqrt{ab}$
3. $4W\sqrt{ab}$
4. $6W\sqrt{ab}$

Q. A ping-pong ball, having a diameter of 3.6 cm and weighing 2.4 g is served with a horizontal velocity of 10 m/sec and a spin that gives rise to a coefficient of lift of 0.2. Assuming the density of air to be 0.00129 gf/cc, the lift experienced by the ball is nearly

1. 13gf
2. 1.3gf
3. 0.13 gf
4. 0.013 gf

Q. Which of the following statements are correct ?
1. Friction and pressure drag depend upon the shape and position of immersed body.
2. If a thin plate is kept parallel to the direction of flow, then the pressure drag is zero.
3.If a thin plate, is kept perpendicular to the moving fluid, then friction drag is zero

1. 1 and 2 only
2. 1 and 3 only
3. 2 and 3 only
4. 1, 2 and 3

Q. The drag coefficient of a car of design condition 60 kmph is to be determined experimentally in a large wing tunnel in a full scale test. The frontal area of the car is $3m^2$. If the force acting on the car in flow direction is measured to be 100 N, then the drag coefficient of car is (take ${\rho }_{air}=1.25kg/m^3$)

1. 0.15
2. 0.2
3. 0.25
4. 0.3

Q. A circular cylinder held in uniform flow from north to south as shown in the figure, is rotated about its own axis in an anticlockwise direction. It will experience a lift force in the direction of

1. N
2. S
3. E
4. W