Answer: Heterogeneous mixture - the parts are not uniformly mixed.
A mixture contains components having distinct chemical properties. There are two types of mixtures: homogeneous and heterogeneous. In a homogeneous mixture there is uniform distribution of components. we cannot distinguish one portion of the mixture from another. for example salt mixed in water. In heterogeneous mixture, the components are not uniformly mixed. hence, we are able to distinguish different parts of a mixture, like the mixture of iron, sand and salt given in this question. 
 
        
                    
             
        
        
        
Explanation:
It is given that,
The acceleration of the toboggan, 
Initial speed of the toboggan, u = 0
We need to find the distance covered by the toboggan. Using the second equation of motion as :

At t = 1 s


At t = 2 s


At t = 3 s


Hence, this is the required solution.
 
        
             
        
        
        
If the input machine produces an
output of 80 Newtons, then the mechanical advantage is that it produces work. If
the required output must be 80 Newtons, then the input force is desirable
having 100 percent production of force even though it requires a large amount
of input to produce 80 Newtons of force.
 
        
             
        
        
        
B. A sandbar is formed by water. A sand dune is formed by wind.