Problem:
The drag force on a boat varies jointly as a wetted area and the square of the velocity of a boat. If a boat going 6.5 mph experiences a drag force of 86 N when the wetted surface area is 41.2 ft², how fast must a boat with 28.5 ft² of wetted surface area goes in order to experience a drag force of 94 N?
Solution:
F = force
A = Area of wetted surface
V = velocity of boat
k = constant of variation
F = 86N ; V = 6.5 mph ; A = 41.2 ft²
F = kAV²
86 = k(41.2)(6.5)²
if
A = 28.5 ft²
F = 94 N
k = 0.049405411616
V = ?
