question_answer

Two pulses in a stretched string whose centres are initially 8 cm apart are moving towards each other as shown in the figure. The speed of each pulse is 2 cm/s. After 2 s, the total energy of the pulses will be

A)  Zero               

B)  Purely kinetic        

C)        Purely potential   

D)   Partly kinetic and partly potential

Correct Answer: B

Solution :

[b] After 2 s, the each wave travels a distance \[=2\,\times 2=4m.\] The wave shape is shown in figure. Thus energy is purely kinetic.