Step 1: Analyze the given 3D hollow geometry (Figure D). It consists of six triangular faces and nine equal edges, forming a symmetrical structure.
Step 2: Identify which given net diagrams (P, Q, R, S) can be folded along the dotted lines to form the described 3D shape.
- Option P: Contains six triangles arranged in a way that they can be folded into a symmetrical 3D figure.
- Option Q: Also consists of six triangles correctly placed for forming the shape.
- Option R: Maintains the same triangular face count and edge arrangement, making it valid.
- Option S: The triangular faces are not arranged correctly to form the required 3D structure.
Step 3: Since P, Q, and R can be folded into the required 3D shape, the correct answer is:
\[ \text{P, Q, and R} \] Thus, the correct answer is option C.
Figure 1 shows the configuration of main scale and Vernier scale before measurement. Fig. 2 shows the configuration corresponding to the measurement of diameter $ D $ of a tube. The measured value of $ D $ is:
The center of a disk of radius $ r $ and mass $ m $ is attached to a spring of spring constant $ k $, inside a ring of radius $ R>r $ as shown in the figure. The other end of the spring is attached on the periphery of the ring. Both the ring and the disk are in the same vertical plane. The disk can only roll along the inside periphery of the ring, without slipping. The spring can only be stretched or compressed along the periphery of the ring, following Hooke’s law. In equilibrium, the disk is at the bottom of the ring. Assuming small displacement of the disc, the time period of oscillation of center of mass of the disk is written as $ T = \frac{2\pi}{\omega} $. The correct expression for $ \omega $ is ( $ g $ is the acceleration due to gravity):