Answer:
light is an example of a wave that is not mechanical . 
it is different as it does not need material medium for its propagation
 
        
             
        
        
        
The SI unit for acceleration is m/s2 ( D)
 
        
             
        
        
        
<span>
At the Earth's surface, warm air expands and rises, creating 
what is known as an area of low pressure.
 Cold air is dense and sinks to the surface to create what is 
known as an area of high pressure.</span>
        
                    
             
        
        
        
Answer:

Explanation:
for the unit vector, we need to divide the given vector by its norm, because it should be in the SAME direction as the original vector, but of magnitude "1".
We notice that the norm of the given vector is:

Then, the unit vector becomes:
