1answer.
Ask question
Login Signup
Ask question
All categories
  • English
  • Mathematics
  • Social Studies
  • Business
  • History
  • Health
  • Geography
  • Biology
  • Physics
  • Chemistry
  • Computers and Technology
  • Arts
  • World Languages
  • Spanish
  • French
  • German
  • Advanced Placement (AP)
  • SAT
  • Medicine
  • Law
  • Engineering
erica [24]
3 years ago
13

Bob can row 14 mph in still water. The total time to travel downstream and return upstream to the starting point is 4 hours. If

the total distance downstream and back is 42 miles, determine the speed of the river (current speed).
Physics
1 answer:
bija089 [108]3 years ago
7 0

Answer:

7 mph

Explanation:

Let the speed of river is c mph.

The effective downstream speed = 14 + c

The effective upstream speed = 14 - c

Total time = 4 hrs

Total distance = 42 miles

Time for upstream + time for downstream = 4 hrs

21 / (14 + c) + 21 / (14 - c) = 4

21 (14 - c + 14 + c) = 4 (196 - c^2)

21 x 28 = 4 (196 - c^2)

c^2 = 196 -147 = 49

c = 7 mph

You might be interested in
The first person to map the Milky Way Galaxy using radio waves was
Art [367]

Answer:B

Explanation:Grote reber was the first scientist to map the milky way galaxy using radio waves.

7 0
2 years ago
Read 2 more answers
In what climates would you expect soil to form fastest? Why?
enyata [817]

Answer:

Soils develop faster in warm, moist climates and slowest in cold or arid ones. Rainfall is one of the most important climate factors in soil formation.

Please mark me brainliest!

Hope this helped God bless :)

5 0
3 years ago
What could serve as ballast for a balloon? Help pls...thx
I am Lyosha [343]
With the advent of the plastic balloon and the beginning of the unmanned ... That would lead to a more sophisticated ballast system that uses fine steel or iron
6 0
3 years ago
If a train is traveling at 85 mph I need to travel 17,000 feet how many hours will it take? Break it down to show the math
Ahat [919]
1 hour for the train to travel 17,000 feet
6 0
3 years ago
A ray of light in air is incident on the mid-point of a heavy flint glass prism surface at an angle of 20º with the normal. for
Nata [24]
Assuming that you have a triangular prism, the ray of light will undergo refraction twice. The first time is the transition from air to flint glass on the entry face, and the second time is the transition from the flint glass to air from the exit face. With the available data, there are two possible solution since saying "20Âş from the normal" isn't enough information. Depending upon which side of the normal that 20 degrees is, the interior triangle will have the angles of 35, 90-r, and 55+r, or 35, 90+r, 55-r degrees where r is the angle from the normal after the 1st refraction. I will provide both possible solutions and you'll need to actually select the correct one based upon the actual geometry which I don't know because you didn't provide the figure or diagram that you were provided with.    

The equation for refraction is:  

(sin a1)/(sin a2) = n1/n2  

where  

a1,a2 = angles from the normal to the surface.  

n1,n2 = index of refraction for the transmission mediums.    

For this problem, we've been given an a1 of 20Âş and an n1 of 1.60. For n2, we will use air which at STP has an index of refraction of 1.00029. So  

(sin a1)/(sin a2) = n1/n2  

(sin 20)/(sin a2) = 1.00029/1.60  

0.342020143/(sin a2) = 0.62518125  

0.342020143 = 0.62518125(sin a2)  

0.547073578 = sin a2  

asin(0.547073578) = a2  

33.16647891 = a2    

So the angle from the normal INSIDE the prism is 33.2Âş. The resulting angle from the surface of the entry face will be either 90-33.2 or 90+33.2 depending upon the geometry. So the 2 possible triangles will be either 35Âş, 56.8Âş, 88.2Âş or 35Âş, 123.2Âş, 21.8Âş. with a resulting angle from the normal of either 1.8Âş or 68.2Âş. I can't tell you which one is correct since you didn't tell me which side of the normal the incoming ray came from. So let's calculate both possible exits.    

1.8Âş  

(sin a1)/(sin a2) = n1/n2  

(sin 1.8)/(sin a2) = 1.6/1.00029  

0.031410759/(sin a2) = 1.599536135  

0.031410759= 1.599536135(sin a2)  

0.019637418= sin(a2)  

asin(0.019637418) = a2  

1.125213477 = a2    

68.2Âş  

(sin a1)/(sin a2) = n1/n2  

(sin 68.2)/(sin a2) = 1.6/1.00029  

0.928485827/(sin a2) = 1.599536135  

0.928485827 = 1.599536135(sin a2)  

0.58047193 = sin a2 

 asin(0.58047193) = a2 

 35.48374252 = a2   

 So if the interior triangle is acute, the answer is 1.13Âş and if the interior triangle is obtuse, the answer is 35.48Âş
5 0
3 years ago
Other questions:
  • Which of the following occurs as light travels farther from its source?
    11·1 answer
  • What is the x component of (+3m)ι^ And (+3m/s) i^?
    6·1 answer
  • You toss a marble straight up into the air with a speed of 1.3 m/s. How long does it take the marble to reach its highest point?
    10·2 answers
  • The amount of fluid displaced by a submerged object depends on its
    6·2 answers
  • Which of the following is a CHEMICAL factor affecting marine biomes?
    13·1 answer
  • If 3.5 paper clips = 1.0 pencils and your paper is 1.5 pencils long, how many paper clips long is your paper?
    12·1 answer
  • A car slows from 22m/s to 3.0m/a at a constant rate of 2.1m/s. How many seconds are required before the car is traveling at 3.0m
    12·1 answer
  • Stems tend to grow in Or against the direction of gravity
    5·1 answer
  • What material was the hindenburg made of?
    5·1 answer
  • In order to go in a circle at a constant speed an object needs
    13·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!