The resistance of a copper wire increases if it is heated and decreases if it is cooled. what will happen to a circuit made of copper wire if the temperature drops from 40°c to 20°c?
a. the current, voltage, and resistance will all increase.
b. the voltage and the resistance will remain constant.
c. the current will increase and the resistance will decrease.
d. the resistance will increase and the voltage will remain constant.

D the resistance will increase. And it will cause current to decrease

I'd say the answer was C. Wire cools, so resistance decreases. Low resistance mean higher current. One possibly spectacular example of this is SUPERCONDUCTIVITY, much used in persistent current carrying coils in hospital imaging equipment, I think.

I'm not sure what your asking buddy.. but i know that you can weld two peices of steel by pure force and pressure.

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.