Two skaters, at rest and facing each other, push off each other. Their initial velocities and momenta are zero, but their final momenta are not. How can
the total initial momentum (which is zero) equal the total final momentum,
since both skaters are now moving? (Remember that momentum is a vector.)
A. This is not an isolated system, so the conservation law does not
apply.
O B. Momentum is not conserved in this case.
O C. The skaters are moving in opposite directions. One momentum is
positive and the other negative, so their values add up to zero.
O D. One skater must be much larger than the other.

1. what is the relationship between wavelength and the penetrating power of an electromagnetic wave? a) the penetrating power has no relationship to the wavelength. b) the penetrating power increases as the wavelength increases. c) the penetrating power decreases as the wavelength increases. d) the penetrating power decreases as the wavelength decreases. 2. as ice melts and turns into water, the speed of sound through the material would most likely do what? justify your answer. a) the speed would not change because the material is always water. b) the speed of sound would increase because the density of water is less than that of ice. c) the speed of sound would increase because energy is added to ice in order to make it melt. d) the speed of sound would decrease because sound travels faster through solids than liquids. 3.which of these waves need a medium to travel through? a) sound b) x-rays c) infrared rays d) visible light