In a circus act, a 20-kg dog is trained to jump onto a 20.0-kg skateboard moving with a velocity of 0.20 m/s. at what velocity does the dog jump into the skateboard if afterward the velocity of the dog and skateboard is -0.20 m/s?

whichever one it is, it's definitely not one that you included on the list you provided.

okay i have so many questions. but the big one here is: um wt..f is this mess? ?

causes

fossil fuels burn

cities become more industrialized

human population grows worldwide

answergravity;