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
tekilochka [14]
3 years ago
9

A boat takes 3.0 hours to travel 50 km down a river, then 5.4 hours to return. Determine the speed of the water in the river.

Physics
1 answer:
Nutka1998 [239]3 years ago
5 0

Answer:

3.7 km/h

Explanation:

Let's call v the proper speed of the boat and v' the speed of the water in the river.

When the boat travels in the direction of the current, the speed of the boat is:

v + v'

And it covers 50 km in 3 h, so we can write

v+v' = \frac{50 km}{3 h}=16.7 km/h (1)

When the boat travels in the opposite direction, the speed of the boat is

v - v'

And it covers 50 km in 5.4 h, so

v-v'=\frac{50 km}{5.4 h}=9.3 km/h (2)

So we have a system of two equations: by solving them simultaneously, we find the value of v and v':

v+v'=16.7 \\v-v'=9.3

Subtracting the second equation from the first one we get:

(v+v')-(v-v')=16.7-9.3\\2v'=7.4\\v'=3.7

So, the speed of the water is 3.7 km/h.


You might be interested in
A ball moving with an initial velocity of 5 m/s comes to rest after 2s. What was the ball's acceleration?
Inga [223]

Answer:

-2.5m/s²

Explanation:

The acceleration of a body is giving by the rate of change of the body's velocity. It is given by

a = Δv / t        ----------------(i)

Where;

a = acceleration (measured in m/s²)

Δv = change in velocity = final velocity - initial velocity   (measure in m/s)

t = time taken for the change (measured in seconds(s))

From the question;

i. initial velocity = 5m/s

final velocity = 0 [since the body (ball) comes to rest]

Δv = 0 - 5 = -5m/s

ii. time taken = t = 2s

<em>Substitute these values into equation (i) as follows;</em>

a = (-5m/s) / (2s)

a = -2.5m/s²

Therefore, the acceleration of the ball is -2.5m/s²

NB: The negative sign shows that the ball was actually decelerating.

6 0
3 years ago
Select the correct answer from each drop-down menu.
-Dominant- [34]

Answer:

And the force of ( Attraction or repulsion) between the poles A and D ( maximum or minimum)

4 0
2 years ago
Read 2 more answers
Mary takes 6.0 seconds to run up a flight of stairs that is 102 meters long. If Mary's weight is 87 newtons, what power has Mary
fredd [130]

Answer: 1479watts

Explanation:

Power is defined as the energy expended or work done in a specific time.

Mathematically,

Power = Workdone/time taken

Since work done is force × distance

Power = force × distance/time

Force = Mary's weight = 87N

Distance = height of the flight = 102meters

Time = 6.0seconds

Substituting in the formula we have;

Power = 87 × 102/6

Power = 1,479watts

Note that the time must be in seconds before usage. If its given in minutes, you will have to convert to seconds

8 0
3 years ago
PLEASE HELP. Really important
Kruka [31]

Explanation:

2) C would need the least effort, because the longer the effort distance, the least the effort applied.

3 0
2 years ago
We need to find the launch velocity of our new marble launcher. we know that it will launch a 25g marble to a distance of 73 cm,
White raven [17]

The launch velocity of the marble launcher is 34.65 m/s

Given that the launch velocity of marble launcher, launches a 25g marble to a distance of 73 cm (0.73 m) and the marble roll up to 6.2 meters before stopping. The launch height is 20 cm (0.2 m).

The time for landing can be calculated by the second equation of motion formula:

h = ut + \frac{1}{2}gt^{2}

Let u = 0

0.2 = 0×t + \frac{1}{2} × 9.8 × t^{2}

t^{2} = \frac{0.2}{4.9}

t^{2} = 0.04

t = 0.2s

Now, the launch velocity of the marble launcher can be calculated by:

Speed = Distance / Time

Speed = \frac{0.73 + 6.3}{0.2}

Speed = \frac{6.93}{0.2}

Speed = 34.65 m/s

Therefore, the launch velocity of the marble launcher is 34.65 m/s

Know more about Launch velocity: -brainly.com/question/18883779

#SPJ9

3 0
1 year ago
Other questions:
  • What waves travel through a medium? Transverse, longitudinal, surface, electromagnetic, and mechanical are the choices
    15·1 answer
  • A cube has a surface area of 54 cm squared. what is its volume
    6·1 answer
  • Given the following frequencies, calculate the corresponding periods. a. 60 Hz b. 8 MHz c. 140 kHz d. 2.4 GHz
    11·1 answer
  • The comparison between work output and work input is
    5·2 answers
  • Which statement below is NOT true about electric field lines?
    5·1 answer
  • Which is true about density?
    15·2 answers
  • When are zeros significant when found to the trailing (to the right) of the decimal point?
    7·1 answer
  • A boy pulls his 9.0 kg sled, applying a horizontal force of 14.0 N (rightward). The coefficient of friction between the snow and
    13·1 answer
  • Excellent human jumpers can leap straight up to a height of
    14·1 answer
  • If a 50 kg box was accelerated to 10 m/s2, how much force was used?
    6·1 answer
Add answer
Login
Not registered? Fast signup
Signup
Login Signup
Ask question!