We can increase the pitch of a sound by
increasing its ?
A. amplitude
B. wavelength
C. wave speed
D. frequency

Which accurately compares concave and convex lenses?

What is the relationship between the direction of motion of the balloon and the wind currents

Arailroad car collides with and sticks to an identical railroad car that is initially at rest. after the collision, the total kinetic energy of the two cars is a) the same as before. b) half as much as before. c) one third as much as before. d) one fourth as much as before. e) twice as much as before.