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.
We need more evidence to be provided
Explanation:
Acceleration is the change in speed over change in time.
a = Δv / Δt
a. The car's acceleration is:
a = (80 km/h − 0 km/h) / 10 s
a = 8 km/h/s
So every second, the speed increases by 8 km/h.
b. The cyclist's acceleration is:
a = (16 m/s − 4.0 m/s) / 5.6 s
a = 2.1 m/s²
c. The stone's speed is:
10.0 m/s² = (v − 0 m/s) / 3.5 s
v = 35 m/s
d. The time is:
1.6 m/s² = (10 m/s − 0 m/s) / t
t = 6.3 s
The amount of energy needed is 2093 J
Explanation:
The amount of energy needed to increase the temperature of a substance by
is given by the equation

where
m is the mass of the substance
C is its specific heat capacity
is the increase in temperature
For the water in this problem, we have
m = 50.0 g = 0.050 kg
(specific heat capacity of water)

Therefore, the amount of energy needed is

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Work needed: 720 J
Explanation:
The work needed to stretch a spring is equal to the elastic potential energy stored in the spring when it is stretched, which is given by

where
k is the spring constant
x is the stretching of the spring from the equilibrium position
In this problem, we have
E = 90 J (work done to stretch the spring)
x = 0.2 m (stretching)
Therefore, the spring constant is

Now we can find what is the work done to stretch the spring by an additional 0.4 m, that means to a total displacement of
x = 0.2 + 0.4 = 0.6 m
Substituting,

Therefore, the additional work needed is

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