Physics Past Questions and Answers

Explain why water in a narrow glass tube has a concave meniscus while mercury, in the same tube, has a convex meniscus.<br/>

State three methods of polarizing an unpolarized light

An electron of charge 1.60 x 10\(^{-19}\) C is accelerated under a potential difference of 1.0 x 10\(^5\) V. Calculate the energy of the electron in joules.

The uncertainty in determining the duration during which an electron remains in a particular energy level before returning to the ground state is 2.0 x 10\(^{-9}\)s. Calculate the uncertainty in determining its energy at that level. (\(\frac{h}{2 \pi}\) = h = 1.054 x 10\(^{-34}\)Js)

(a) What is a vector quantity?<br/>(b) Three vectors 3 ms\(^{-1}\) N 45° W, 12 ms\(^{-1}\)W and 5 ms\(^{-1}\)S act at a point.<br/>(i) Sketch a vector diagram to illustrate the given information.<br/>(ii) Calculate the resultant of the vectors.<br/>(c) In a laboratory experiment to determine the force constant of a spiral spring, the mass or, the spring was varied and the corresponding extensions were measured and recorded as shown in the table below.<br/><table class='tbn'><tbody><tr><td> Mass M/g </td><td> Weight W/N </td><td> Extension e/cm </td></tr><tr><td> 50100150200250 </td><td> </td><td> 6.511.015.020.025.0 </td></tr></tbody></table><br/><br/><br/>(i) Copy and complete the table. (Take g = 10 ms\(^{-2}\))<br/>(ii) Plot a graph with weight, W, on the vertical axis and extension, e, on the horizontal axis.<br/>(iii) Using the graph, determine the force constant of the spring.<br/>(iv) Determine the natural length of the spring if its length was 38.0 cm when loaded with 250 g mass.