What can be correctly concluded from this experiment?

John has a boat that will travel at the rate of 15 kph in still water. he can go upstream for 35 km in the same time it takes to

MA_775_DIABLO [31]

Let F = the downstream speed of the water.

Then the boat's upstream speed is: 15 - F 
The boat's downstream speed is: 15 + F 

Assume both the journeys mentioned take T hours, then using "speed x time = distance" we get: 

Downstream journey: (15 + F)T = 140 
Upstream journey: (15 - F)T = 35 

Add the two formulae together: 

(15 + F)T + (15 - F)T = 140 + 35 

15T + FT + 15T - FT = 175 

30T = 175 

T = 35/6 

Use one of the equations to find F: 

(15 + F)T = 140 

15 + F = 140/T 
F = 140/T - 15 
F = 140/(35/6) - 15 
F = 24 - 15 
F = 9 

i.e. the downstream speed of the water is 9 kph 

Therefore, the boat's speed downstream is 15 + F = 15 + 9 = 24 kph.
the answer is: *24kph*

5 0

2 years ago

A 0.250 kg block on a vertical spring with spring constant of 4.45 ✕ 103 N/m is pushed downward, compressing the spring 0.080 m.

Elza [17]

Answer:h=5.81 m

Explanation:

Given

Mass of block(m)=0.250 kg

Spring Constant $k=4.45\times 10^3 N/m$

Initial elongation =0.080 m=8 cm

Thus Initial Potential Energy stored =Final Potential Energy stored in Block

$P_i=\frac{kx^2}{2}$

$P_i=\frac{4.45\times 10^3\times 64\times 10^{-4}}{2}=14.24 J$

$P_f=mgh=0.25\times 9.8\times h$

$P_i=P_f$

$14.24 =0.25\times 9.8\times h$

$h=\frac{14.24}{0.25\times 9.8}=5.81 m$

6 0

2 years ago

I NEED HELP!!!!!!!!!!!

nadezda [96]

1. 168.1 Hz

To find the apparent frequency heard by the driver in the car, we can use the formula for the Doppler effect:

$f'=(\frac{v\pm v_o}{v\pm v_s})f$

where

f is the original sound of the horn

v is the speed of sound

$v_o$ is the velocity of the observer (the driver and the car), which is positive if the observer is moving towards the source and negative if it is moving away

$v_s$ is the velocity of the sound source (the train), which is positive if the source is moving away from the observer and negative otherwise

In this problem we have, according to the sign convention used:

$v = 343 m/s\\f = 164 Hz\\v_o = -15 m/s\\v_s = -23 m/s$

Substituting, we find:

$f'=(\frac{343-15}{343-23})(164)=168.1 Hz$

2. $2.96\cdot 10^8 m/s$

The speed of light can be calculated as

$v=\frac{d}{t}$

where

d is the distance travelled

t is the time taken

In this problem:

$d=2\cdot 3.85\cdot 10^8 =7.7\cdot 10^8 m$ is the total distance travelled by the laser beam (twice the distance between the Earth and the Moon)

t = 2.60 s is the time taken

Substituting in the formula,

$v=\frac{7.7\cdot 10^8 m}{2.60 s}=2.96\cdot 10^8 m/s$

6 0

2 years ago

Bats use a process called echolocation to find their food. This involves giving out sound waves that hit possible prey or food.

cupoosta [38]

The type of waves used by bats are sound waves. Most of the species use their larynx to produce ultrasound waves in the frequency range of 20 to 200 kilohertz.
These sound waves are echoed, reflected, by surroundings, in this case food or prey. These reflections are received by the specialized receptor cells in the ears of bats. The reflections are analyzed by the brain to make an image.
Fun fact: The brain cells of bats are also specialized to better analyze the frequency of ultrasound used by the bat.

8 0

2 years ago

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Which of the following is NOT true of electromagnetic waves? A. An electric field is created in any region of space in which a m

Iteru [2.4K]

The incorrect statement about electromagnetic waves is C. induction of electric fields by changing magnetic fields only occurs if a conducting material is present.
Electromagnetic waves do not rely on any medium for propagation, which means that the generation of fields is irrespective of the presence of a conducting material.

6 0

2 years ago

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