Finding distance and momentum

1) The speed of a sound in human tissue is about 1600m/s. If an ultrasound pulse takes 1.5x10 to the power of -5 to travel through a tissue, what is the thickness of the tissue?


#2) A 0.500 kg ball with a speed of 4.0 m/s strikes a stationary 1.0 kg target. If momentum is conserved, what is the total momentum of the ball and target after the collision?

speed = distance/ time
d = v * t
= 1600 * 1.5 * 10 ^ -5
= 0.024 m

or 2.4 cm


Momentum is always conserved.
Momentum = m * v

Prior to the collision
the ball has a momentum of 0.500 * 4 = 2Kgm/s
and the target is not moving so it has no momentum

The total momentum is 2 Kg m/s and this must also be the momentum after the collision because momentum is conserved.