when the combustion engine was invented it had many positive effects on society, but years later it has been discovered that the burning of oil and coal has one major negative effect on the environment. what is that negative effect?

Several negative effects of the combustion engine are : 
- It Defects air quality
- It uses nonrenewable Resources ( which means that one day the resource will be extinct)
- It causes holes in the ozone which will lead to increase in earth temperature

hope this helps

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.