A blue train of mass 50 kg moves at 4 m/s toward a green train of 30 kg initially at rest. The trains collide. After the collision the green train moves with a speed of 3 m/s. What is the final speed of the blue train? A. 3.4 m/s
B. 1.6 m/s
C. 5 m/s
D. 2.2 m/s

Which explanation describes the forces involved for a person to walk down the sidewalk? a. the person's feet push backward on the sidewalk; the sidewalk pushes backward on the person. b. the person's feet push forward on the sidewalk; the sidewalk does not push on the person. c. the person's feet push backward on the sidewalk; the sidewalk pushes forward on the person. d. the person's feet push forward on the sidewalk; the sidewalk pushes forward on the person.

Wavelength,frequency,and energy are related.what happens to a wave as it’s wavelength gets shorter?

What is the speed of an object at a given moment?