In this item, we let x be the rate of the boat in still water and y be the rate of the current.
Upstream. When the boat is going upstream, the speed in still water is deducted by the speed of the current because the boat goes against the water. The distance covered is calculated by multiplying the number of hours and the speed.
(x - y)(3) = 144
Downstream. The speed of the boat going downstream is equal to x + y because the boat goes with the current.
(x + y)(2) = 144
The system of linear equations we can use to solve for x is,
3x - 3y = 144
2x + 2y = 144
We use either elimination or substitution.
We solve for the y of the first equation in terms of x,
y = -(144 - 3x)/3
Substitute this to the second equation,
2x + 2(-1)(144 - 3x)/3 = 144
The value of x from the equation is 60
<em>ANSWER: 60 km/h</em>
Answer:
a An increase in the speed will lower the internal pressure
Explanation:
Bernoulli's fluid formula

where
P = Pressure
ρ = Density of fluid
g = Acceleration due to gravity
h = Height
v = Velocity of fluid
If there is no change in height then we get

According to the Bernoulli's principle when the speed of the fluid is larger in a region of streamline flow the pressure is smaller in that region. From the above equation it can be seen that increase in speed should simultaneously reduce pressure in order for their sum to be constant.