Message:
Dad, I missed the bus. I need your bike to attend my entrance test. I know you're on your morning walk, but please come back soon so I can leave. I’ll wait for you in the living room. Thanks!
Explain the construction of a spherical wavefront by using Huygens' principle.
The perpendicular distance of the plane \( r \cdot (3\hat{i} + 4\hat{j} + 12\hat{k}) = 78 \) from the origin is __________.
Derive an expression for maximum speed of a vehicle moving along a horizontal circular track.