11 NCERT Physics Most Important Questions

Q1. A tuning fork gives 3 beats per second with sonometer wire when its length is either 49.8 cm of 50.2 cm.  Find the frequency of tuning fork. Solution Let v, v 1 and v 2 be the frequencies of tuning fork and sonometer wire when its length is 49.8 cm and 50.2 cm respectively.  As frequency of sonometer wire is inversely proportional to length of the sonometer wire, therefore, Q2. A bat emits ultrasonic sound of frequency 100 kHz in air.  If this sound meets a water surface, what is the wavelength of (i)  the reflected sound, (ii)  the transmitted sound?  Speed of sound in air = 340 ms -1 and in water = 1486 ms -1 . Solution Q3. An engine approaches a high vertical wall with constant speed of 90 m/sec.  When it is at a distance of 1050 m from the wall, it blows a whistle, whose echo is heard after 5 second.  Calculate the speed of sound in air. Solution Let V be the velocity of sound and u be the velocity of source an...

Q1. What will be the period of oscillation of a simple pendulum of length 100 cm in a spaceship in a geostationary orbit? Solution In any satellite orbiting the Earth (in any orbit), the condition of weightlessness exists (i.e. effective g = 0). Hence, the pendulum does not oscillate and its period is therefore infinity. Q2. Which of the following functions of time represent : (a) simple harmonic (b) periodic but not simple harmonic (c)  non-periodic motion? where k is a real positive constant. (i)  sin kt+cos kt (ii) 2 sin 2 kt (iii) e -kt (iv) log kt Solution Q3. Two identical, springs each of spring factor K, may be connected in the following different ways.. Deduce the spring factor for oscillations of the body P of mass m in each case. Solution (a) Let the mass of the body P be m. Suppose an extension x is produced in the spring when a force mg is applied to it. The equilibrium position is given by: F = mg = kx         ...