Physics Questions and Answers

A ship travelling towards a cliff receives the echo of its whistle after 3.5 seconds. A short while later, it receives the echo after 2.5 seconds. If the speed of sound in air under the prevalling condition is 250ms -1, how much closer is the ship to the cliff?

The refractive index of a liquid is 1.5. If the velocity of light in vacuum is 3.0 x 10$^8ms^{-1}$, the velocity of light in the liquid is 

Consider the three forces acting at O and in equilibrium as shown in the figure. Which of the following equations is/are CORRECT?

I. P$_1$ cos $\theta_1$ = p$_1$ cos $\theta_2$

II. P$_3$ = P$_1$ cos $\theta_4$  + P$_2 cos_2$

III. P$_1 \sin \theta_1 = P_2 \sin \theta_2$

A hydrometer is an instrument for measuring the 

A magnetic needle is suspended first at the earth's north magnetic pole and then at a point on the magnetic equator. The respective angles between the needle and the horizontal are