Take r vector to be in the direction of k vector.
Now, take kx-wt=A (some constant phase) and differentiate it with respect to t . you get dx/dt=w/k which is the velocity of the point whose A(phase) is constant, and hence velocity of wave . It is called phase velocity. Direction of the...
Frictional force depends upon contact between two materials. It arises due to electromagnetic interaction between the atoms of two materials. See http://www.actionurl.com/ia9fh
PS: there are plenty of graphic softwares for creating images like inclined planes. Try MS paint, adobe photoshop etc.