The car approaches a stationary observer and so the sound will appear to have shorter wavelength. This creates an effect of its siren to sound with higher frequency than it would do if both were stationary.

(7) The Doppler formula for frequency in the case of a stationary observer and source approaching it is as follows:

$f_O = \frac{v}{v-v_s}\cdot f= \frac{343\frac{m}{s}}{(343-25)\frac{m}{s}}\cdot 400Hz \approx 431Hz$

The wavelength is then

$\lambda = \frac{343\frac{m}{s}}{431Hz}\approx 0.80 m$

The third choice "0.80m; 431Hz" is correct

7 0

3 years ago

A rectangular beam 10 cm wide, is subjected to a maximum shear force of 50000 N, the corresponding maximum shear stress being 3

nika2105 [10]

Answer:

Option B is the correct answer.

Explanation:

Shear stress is the ratio of shear force to area.

We have

Shear stress = 3 N/mm² = 3 x 10⁶ N/m²

Area = Area of rectangle = 10 x 10⁻² x d = 0.1d

Shear force = 50000 N

Substituting

$\texttt{Shear stress}=\frac{\texttt{Shear force}}{\texttt{Area}}\\\\3\times 10^6=\frac{50000}{0.1d}\\\\d=0.1667m=16.67cm$

Width of beam = 16.67 cm

Option B is the correct answer.

6 0

3 years ago