An object is said to have an n-fold rotational symmetry if the object, rotated by an angle of \( \frac{2\pi}{n} \), is identical to the original.
Which one of the following objects exhibits 4-fold rotational symmetry about an axis perpendicular to the plane of the screen?




Understanding Rotational Symmetry: Rotational symmetry refers to an object's ability to look the same after being rotated by a certain angle about a fixed point or axis.
4-Fold Rotational Symmetry: An object has 4-fold rotational symmetry if it looks identical after each 90-degree rotation.
Analysis of Options:
Conclusion: The object in option (B) exhibits 4-fold rotational symmetry about the axis perpendicular to the plane of the screen.
Key Insight: The key to identifying rotational symmetry is to rotate the object by the specified angle and check if it aligns with its original position at each step. If it does, it possesses that level of symmetry.

Consider a reinforced concrete beam section of 350 mm width and 600 mm depth. The beam is reinforced with the tension steel of 800 mm\(^2\) area at an effective cover of 40 mm. Consider M20 concrete and Fe415 steel. Let the stress block considered for concrete in IS 456:2000 be replaced by an equivalent rectangular stress block, with no change in (a) the area of the stress block, (b) the design strength of concrete (at the strain of 0.0035), and (c) the location of neutral axis at flexural collapse.
The ultimate moment of resistance of the beam (in kN.m) is ___________ (round off to the nearest integer).
Two soils of permeabilities \( k_1 \) and \( k_2 \) are placed in a horizontal flow apparatus, as shown in the figure. For Soil 1, \( L_1 = 50 \, {cm} \), and \( k_1 = 0.055 \, {cm/s} \); for Soil 2, \( L_2 = 30 \, {cm} \), and \( k_2 = 0.035 \, {cm/s} \). The cross-sectional area of the horizontal pipe is 100 cm², and the head difference (\( \Delta h \)) is 150 cm. The discharge (in cm³/s) through the soils is ........ (rounded off to 2 decimal places).

The most suitable test for measuring the permeability of clayey soils in the laboratory is ___________.
Consider the beam ACDEB given in the figure. Which of the following statements is/are correct:
