NCERT Class 11 Physics Solutions: Chapter 15 – Waves-Part 1

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Question 15.1:

A string of mass is under a tension of . The length of the stretched string is . If the transverse jerk is struck at one end of the string, how long does the disturbance take to reach the other end?

Answer:

Mass of the string,

Tension in the string,

Length of the string,

Mass per unit length,

The velocity of the transverse wave in the string is given by the relation:

Time taken by the disturbance to reach the other end,

Question 15.2:

A stone dropped from the top of a tower of height high splashes into the water of a pond near the base of the tower. When is the splash heard at the top given that the speed ? ( )

Answer:

Height of the tower,

Initial velocity of the stone,

Acceleration,

Speed of sound in air

The time taken by the stone to strike the water in the pond can be calculated using the second equation of motion, as:

Time taken by the sound to reach the top of the tower,

Therefore, the time after which the splash is heard,

Question 15.3:

A steel wire has a length of and a mass of . What should be the the wire so that speed of a transverse wave on the wire equals the speed of sound in dry air at

Answer:

Length of the steel wire,

Mass of the steel wire,

Velocity of the transverse wave,

Mass per unit length,

For tension, velocity of the transverse wave can be obtained using the relation: