The velocity of the wave involved in the Doppler effect:

The change in the frequency of the musical pitch implies a speed of around 40 meters per second, and the smallest changes in the frequency can be easily with changes in the amplitude of sounds.

need to see circuit to get time constant

the chart show the masses and velocities of two colliding objects that stick together after a collision.

according to the law of conservation of momentum, the momentum of the object after the collision is  

answer

1,500

kg • m/s.