Shown below is a large block 64 cm wide, 48 cm long, and 8.0 cm high. This block

Question

Shown below is a large block 64 cm wide, 48 cm long, and 8.0 cm high. This block is passing through air (density ? = 1.43 kg/m3) at a speed of v = 8.76 m/s.

1) Find the drag force Fd acting on the block if it is traveling in the direction illustrated with the velocity vector v1 with a drag coefficient ? = 0.862.

2) Find the drag force acting on the block if it is traveling in the direction illustrated with the velocity vector v2 with a drag coefficient ? = 0.948.

3) Find the drag force acting on the block if it is traveling in the direction illustrated with the velocity vector v3 with a drag coefficient ? = 1.12.

Explanation / Answer

FD = 0.5*rho*v^2*tau*A
where tau = drag coefficient
rho=density

1)
v= 8.76 m/s
rho = 1.43 kg/m^3
tau = 0.862
A = 0.64*0.08 m^2 =0.0512 m^2

FD = 0.5*rho*v^2*tau*A
= 0.5*(1.43)*(8.76)^2*0.862*0.0512
= 2.42 N

2)
v= 8.76 m/s
rho = 1.43 kg/m^3
tau = 0.948
A = 0.48*0.08 m^2 =0.0384 m^2

FD = 0.5*rho*v^2*tau*A
= 0.5*(1.43)*(8.76)^2*0.948*0.0384
= 2.00 N

3)
v= 8.76 m/s
rho = 1.43 kg/m^3
tau = 1.12
A = 0.64*0.48 m^2 =0.3072 m^2

FD = 0.5*rho*v^2*tau*A
= 0.5*(1.43)*(8.76)^2*1.12*0.3072
= 18.9 N

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