Answer:
Rectangular path
Solution:
As per the question:
Length, a = 4 km
Height, h = 2 km
In order to minimize the cost let us denote the side of the square bottom be 'a'
Thus the area of the bottom of the square, A = 
Let the height of the bin be 'h'
Therefore the total area, 
The cost is:
C = 2sh
Volume of the box, V =
(1)
Total cost,
(2)
From eqn (1):

Using the above value in eqn (1):


Differentiating the above eqn w.r.t 'a':

For the required solution equating the above eqn to zero:


a = 4
Also

The path in order to minimize the cost must be a rectangle.
Answer:
|F| = 393750 N
Explanation:
Given that,
Total mass of the train, m = 750000 kg
Initial speed, u = 84 m/s
Final speed, v = 42 m/s
Time, t = 80 s
We need to find the net force acting on the train. The formula for force is given by :
F = ma

So, the magnitude of net force is 393750 N.
Answer:
Bowling Ball
Explanation:
The potential energy depends on the factors: mass of the object and distance between the two objects. In this case the distance is between the ground and the balls. Here, the bowling ball is heaviest and its center of mass is farthest in comparison to other two balls. Thus, it has the greatest potential energy.