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vfiekz [6]
2 years ago
12

To qualify to run in the 2005 boston marathon, a distance of 26.2 miles, an 18-year-old woman had to have completed another mara

thon in 3 hours and 40 minutes or less. to qualify, what must a woman's average speed have been in miles per hour?
Physics
2 answers:
Kisachek [45]2 years ago
7 0

Answer:

The woman's average speed must have been 7.14miles/hour. This is the ratio of the total distance she covered/traveled to the total time it took her to cover that distance.

Explanation:

Here is the calculation,

Total distance = 26.2miles

Total time = 3hours and 40min.

40min = (40min/60min) × 1hour = 0.67hour. This is basically converting time in mins to time in hours.

Therefore total time taken = 3hours and 40mins = 3 hours + 0.67 hours = 3.67hours

Average speed = Total distance/Total time taken

Average speed = 26.2miles/3.67 hours = 7.14 miles/hour

oksian1 [2.3K]2 years ago
5 0
3 hours and 40 minutes is equivalent to 3.667 hours. If a woman must have run another marathon (of 26.2 miles) within that time, then her minimum average speed in mph can be calculated by dividing the distance by time:
26.2 miles / 3.667 hours = 7.145 miles per hour
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A small box of mass m1 is sitting on a board of mass m2 and length L. The board rests on a frictionless horizontal surface. The
Nadusha1986 [10]

Answer:

The constant force with least magnitude that must be applied to the board in order to pull the board out from under the box is \left( {{m_1} + {m_2}} \right){\mu _{\rm{s}}}

Explanation:

The Newton’s second law states that the net force on an object is the product of mass of the object and final acceleration of the object. The expression of newton’s second law is,

\sum {F = ma}

Here, is the sum of all the forces on the object, mm is mass of the object, and aa is the acceleration of the object.

The expression for static friction over a horizontal surface is,

F_{\rm{f}}} \leq {\mu _{\rm{s}}}mg

Here, {\mu _{\rm{s}}} is the coefficient of static friction, mm is mass of the object, and g is the acceleration due to gravity.

Use the expression of static friction and solve for maximum static friction for box of mass {m_1}

Substitute  for in the expression of maximum static friction {F_{\rm{f}}} = {\mu _{\rm{s}}}mg

{F_{\rm{f}}} = {\mu _{\rm{s}}}{m_1}g

Use the Newton’s second law for small box and solve for minimum acceleration aa to pull the box out.

Substitute  for , [/tex]{m_1}[/tex] for in the equation .

{F_{\rm{f}}} = {m_1}a

Substitute {\mu _{\rm{s}}}{m_1}g for {F_{\rm{f}}} in the equation {F_{\rm{f}}} = {m_1}a

{\mu _{\rm{s}}}{m_1}g = {m_1}a

Rearrange for a.

a = {\mu _{\rm{s}}}g

The minimum acceleration of the system of two masses at which box starts sliding can be calculated by equating the pseudo force on the mass with the maximum static friction force.

The pseudo force acts on in the direction opposite to the motion of the board and the static friction force on this mass acts in the direction opposite to the pseudo force. If these two forces are cancelled each other (balanced), then the box starts sliding.

Use the Newton’s second law for the system of box and the board.

Substitute for for in the equation .

{F_{\min }} = \left( {{m_1} + {m_2}} \right)a

Substitute for in the above equation .

{F_{\min }} = \left( {{m_1} + {m_2}} \right){\mu _{\rm{s}}}g

The constant force with least magnitude that must be applied to the board in order to pull the board out from under the box is \left( {{m_1} + {m_2}} \right){\mu _{\rm{s}}}g

There is no friction between the board and the surface. So, the force required to accelerate the system with the minimum acceleration to slide the box over the board is equal to total mass of the board and box multiplied by the acceleration of the system.

5 0
3 years ago
The human ear canal is about 2.6 cm long and can be regarded as a tube open at one end and closed at the eardrum. What is the fu
Ugo [173]

Answer:

f = v/λ

 = v/4*L

 = 343 / 4 (0.026)

= 3120 Hz  

8 0
3 years ago
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If two stars are the same size and one is twice the temperature of the other, how much more luminous is the hotter one? quizlit
Dmitriy789 [7]
The hotter star will be 16 times more luminous  - luminosity depends on two things  - the size of the star and the temperature of the star. The hotter a star is, the more energy it will give out. This will give rise to greater luminosity.
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3 years ago
Choose the correct statement regarding the sign conventions for lenses.
Savatey [412]

Answer:

a) false

b) True

c) True

d) False

e) False

Explanation:

a) False

For a diverging lens, the focal length is negative while it is positive for a converging lens

b) True

Image distances  for virtual images are always negative and it also forms on the the same side of the lens as the object and is enlarged

c) True

d) False

For a diverging lens, the focal length is negative while it is positive for a converging lens

e) False

Image distances  for virtual images are always negative and it also forms on the the same side of the lens as the object and is enlarged

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Angelina_Jolie [31]

Solution :

Frequency may be defined as the number of observation or number of waves that is taken in per unit time. The unit of frequency is Hertz or Hz.

It is given that :

Successive harmonic frequencies, f = 52.2 Hz

and f' = 60.9 Hz

Therefore, fundamental frequency, F = f' - f

                                                           F = 60.9 - 52.2

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Therefore the string which is fixed at both the ends forms all the harmonics.

6 0
2 years ago
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