2. What is the cart's displacement from 0 seconds to 7 seconds?

You need to be more specific.  i really don't know what a "motion map" is.you can draw a graph of an object's position, distance, displacement, speed,velocity, or acceleration versus time, or you can draw a graph of the object's x-position versus its y-position and not give any information about time at all.if the graph presents position or displacement against time,  then constant velocity is a straight line . . i.e. a line that has  constant slope.if the graph shows speed against time, then constant velocityis a horizontal piece of line.if the graph shows acceleration against time, then constant  velocity is a piece of line that lies on the x-axis . . it's value is zero. 

Answerthe valence of an element or radical is equal to the number of positive or negative charges on the ion.

Hellosubatomic particles  are  particles  that are smaller than the atom. protons, neutrons, and electrons are the three mainsubatomic particles  found in an atom. protons have a positive (+)  charge. an easy way to remember this is to remember that both neutron and no  electrical charge  start with the letter "n."have a nice day