We now have the tools to solve the problem we introduced in the opening of the section.
An airplane is flying at an airspeed of 200 miles per hour headed on a SE bearing of 140°. A north wind (from north to south) is blowing at 16.2 miles per hour. What are the ground speed and actual bearing of the plane? See
[link] .
The ground speed is represented by
in the diagram, and we need to find the angle
in order to calculate the adjusted bearing, which will be
Notice in
[link] , that angle
must be equal to angle
by the rule of alternating interior angles, so angle
is 140°. We can find
by the Law of Cosines:
The ground speed is approximately 213 miles per hour. Now we can calculate the bearing using the Law of Sines.
Therefore, the plane has a SE bearing of 140°+2.8°=142.8°. The ground speed is 212.7 miles per hour.
The position vector has its initial point at the origin. See
[link] .
If the position vector is the same for two vectors, they are equal. See
[link] .
Vectors are defined by their magnitude and direction. See
[link] .
If two vectors have the same magnitude and direction, they are equal. See
[link] .
Vector addition and subtraction result in a new vector found by adding or subtracting corresponding elements. See
[link] .
Scalar multiplication is multiplying a vector by a constant. Only the magnitude changes; the direction stays the same. See
[link] and
[link] .
Vectors are comprised of two components: the horizontal component along the positive
x -axis, and the vertical component along the positive
y -axis. See
[link] .
The unit vector in the same direction of any nonzero vector is found by dividing the vector by its magnitude.
The magnitude of a vector in the rectangular coordinate system is
See
[link].
In the rectangular coordinate system, unit vectors may be represented in terms of
and
where
represents the horizontal component and
represents the vertical component. Then,
v = a
i + b
j is a scalar multiple of
by real numbers
See
[link] and
[link] .
Adding and subtracting vectors in terms of
i and
j consists of adding or subtracting corresponding coefficients of
i and corresponding coefficients of
j . See
[link] .
A vector
v =
a
i +
b
j is written in terms of magnitude and direction as
See
[link] .
The dot product of two vectors is the product of the
terms plus the product of the
terms. See
[link] .
We can use the dot product to find the angle between two vectors.
[link] and
[link] .
Dot products are useful for many types of physics applications. See
[link] .
Wayne and Dennis like to ride the bike path from Riverside Park to the beach. Dennis’s speed is seven miles per hour faster than Wayne’s speed, so it takes Wayne 2 hours to ride to the beach while it takes Dennis 1.5 hours for the ride. Find the speed of both bikers.
from theory: distance [miles] = speed [mph] × time [hours]
info #1
speed_Dennis × 1.5 = speed_Wayne × 2
=> speed_Wayne = 0.75 × speed_Dennis (i)
info #2
speed_Dennis = speed_Wayne + 7 [mph] (ii)
use (i) in (ii) => [...]
speed_Dennis = 28 mph
speed_Wayne = 21 mph
George
Let W be Wayne's speed in miles per hour and D be Dennis's speed in miles per hour. We know that W + 7 = D and W * 2 = D * 1.5.
Substituting the first equation into the second:
W * 2 = (W + 7) * 1.5
W * 2 = W * 1.5 + 7 * 1.5
0.5 * W = 7 * 1.5
W = 7 * 3 or 21
W is 21
D = W + 7
D = 21 + 7
D = 28
Salma
Devon is 32 32 years older than his son, Milan. The sum of both their ages is 54 54. Using the variables d d and m m to represent the ages of Devon and Milan, respectively, write a system of equations to describe this situation. Enter the equations below, separated by a comma.
please why is it that the 0is in the place of ten thousand
Grace
Send the example to me here and let me see
Stephen
A meditation garden is in the shape of a right triangle, with one leg 7 feet. The length of the hypotenuse is one more than the length of one of the other legs. Find the lengths of the hypotenuse and the other leg
however, may I ask you some questions about Algarba?
Amoon
hi
Enock
what the last part of the problem mean?
Roger
The Jones family took a 15 mile canoe ride down the Indian River in three hours. After lunch, the return trip back up the river took five hours. Find the rate, in mph, of the canoe in still water and the rate of the current.
Shakir works at a computer store. His weekly pay will be either a fixed amount, $925, or $500 plus 12% of his total sales. How much should his total sales be for his variable pay option to exceed the fixed amount of $925.
I'm guessing, but it's somewhere around $4335.00 I think
Lewis
12% of sales will need to exceed 925 - 500, or 425 to exceed fixed amount option. What amount of sales does that equal? 425 ÷ (12÷100) = 3541.67. So the answer is sales greater than 3541.67.
Check:
Sales = 3542
Commission 12%=425.04
Pay = 500 + 425.04 = 925.04.
925.04 > 925.00
Munster
difference between rational and irrational numbers
Jazmine trained for 3 hours on Saturday. She ran 8 miles and then biked 24 miles. Her biking speed is 4 mph faster than her running speed. What is her running speed?