Two points A and B on the opposite banks of a river line AB the distan...
Problem Statement:
Two points A and B are located on opposite banks of a river. The distance between points A and B is 280 m. The velocity of the river current v = 60 m/s and is constant throughout the width of the river. The line AB makes an angle α = 53 degrees with the direction of the current. The angle β remains the same during the passage from A to B and from B to A. The velocity U and angle β needed to cover the distance AB and return in time T = 128 seconds are to be determined.
Solution:
To determine the required velocity U and angle β, we can break down the motion of the boat into horizontal and vertical components.
Horizontal Component:
The horizontal component of the boat's velocity is responsible for the motion across the river. Let's denote this component as Vh. The velocity of the river current is given as v = 60 m/s. Since the boat's motion is perpendicular to the river current, the horizontal component of the boat's velocity can be written as:
Vh = U * cos(β)
Vertical Component:
The vertical component of the boat's velocity is responsible for the motion along the river. Let's denote this component as Vv. The velocity of the river current is given as v = 60 m/s. Since the boat's motion is parallel to the river current, the vertical component of the boat's velocity can be written as:
Vv = v + U * sin(β)
Time of Travel:
To determine the required velocity U and angle β, we need to consider the time taken to travel from point A to point B and back to point A. The total time of travel is given as T = 128 seconds.
The time taken to travel from point A to point B can be calculated using the horizontal component of the boat's velocity:
t1 = 280 / Vh
The time taken to travel from point B to point A can be calculated using the vertical component of the boat's velocity:
t2 = 280 / Vv
The total time of travel is the sum of t1 and t2:
T = t1 + t2
Equation for Total Time:
Substituting the expressions for Vh and Vv in terms of U and β, we can write the equation for the total time of travel as:
T = (280 / (U * cos(β))) + (280 / (v + U * sin(β)))
Finding U and β:
To solve for U and β, we need to solve the equation T = (280 / (U * cos(β))) + (280 / (v + U * sin(β))) for U and β.
This equation can be solved numerically using numerical methods or through trial and error. By iterating and adjusting the values of U and β, we can find the values that satisfy the equation and give us a total time of travel equal to T = 128 seconds.
Once the values of U and β are determined, the boat can cover the distance AB and return in time T = 128 seconds by maintaining a velocity U and an angle β with respect to the line AB.