Question

An air chamber of volume V has a neck of cross-sectional area a into which a light ball of mass m can move without friction. The diameter of the ball is equal to that of the neck of the chamber. The ball is pressed down a little and released. If the bulk modulus of air in B, the time period of the resulting oscillation of the ball is given by 

Solution

Correct option is

 

Let P be the pressure of air in the chamber. When the ball is pressed down a distance x, the volume of air decreased from V to say V – ∆V. Hence the pressure increases from P to P + ∆P. The change in volume (see fig) is   

                   

The excess pressure ∆P is related to the bulk modulus B

   

now restoring force on ball = excess pressure × cross-sectional area

  

            

Hence the motion of the ball is simple harmonic. If m is the mass of the ball, the time period of the SHM is

              

SIMILAR QUESTIONS

Q1

A spring stretches by 0.05 m when a mass of 0.5 kg is hung from it. A body of mass 1.0 kg is attached to one of its ends, the other end being fixed to the wall. The body is pulled 0.01 m along a horizontal frictionless surface and released. What is the total energy of the oscillator. Assume the string to have negligible mass and take g = 10 ms–2.  

Q2

A spring of negligible mass having a force constant k extends by an amount y when a mass m is hung from it. The mass is pulled down a little and released. The system begins to execute simple harmonic motion of amplitude A and angular frequency ω. The total energy of the mass-spring system will be

Q3

A spring has a natural length of 50 cm and a force constant of  A body of mass 10 kg is suspended from it and the spring is stretched. If the body is pulled down further stretching the spring to a length of 58 cm and released, it executes simple harmonic motion. What is the net force on the body when it is at its lowermost position of its oscillation? Take g = 10 ms –2.

Q4

A small trolley of mass 2 kg resting on a horizontal frictionless turntable is connected by a light spring to the centre of the table. The relaxed length of the spring is 35 cm. When the turntable is rotated an angular frequency of 10 rad s–1, the length of the spring becomes 40 cm. what is the force constant of the spring?  

Q5

Two springs of force constants k1 and k2 are connected to a mass mplaced on a horizontal frictionless surface as shown in fig (a) and (b). What is the ratio of the time periods of horizontal oscillation in cases (a) and (b) if k1 = k2?

                                                      

Q6

Two springs of force constants k1 and k2 are connected to a mass m as shown in fig (a) and (b). What is the ratio of the time periods of vertical oscillation in cases (a) and (b) if k1 = k2?

                                        

Q7

A tray of mass M = 10 kg is supported on two identical springs, each of spring constant k, as shown in fig. When the tray is depressed a little and released, it executes simple harmonic motion of period 1.5 s. When a block of mass m is placed on the tray, the period of oscillation becomes 3.0 s. The value of m is  

                                                                 

Q8

A vertical U-tube of uniform cross-sectional area A contains a liquid of density ρ. The total length of the liquid column in the tube is L. The liquid column is disturbed by gently blowing into the tube. If viscous effects are neglected, the time period of the resulting oscillation of the liquid column is given by 

Q9

A cylindrical piece of cork of height h and density ρc floats vertically in a liquid of density ρl. The cork is depressed slightly an released. If viscous effects are neglected, the time period of vertical oscillations of the cylinder is given by

Q10

A simple pendulum of length l and bob mass m is displaced from its equilibrium position O to a position P so that the height of P above O is h. It is then released. What is the tension in the string when the bob passes through the equilibrium position O? Neglect friction. V is the velocity of the bob at O.