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Romashka-Z-Leto [24]
3 years ago
10

A 60-kg runner raises his center of mass approximately 0.5 m with each step. Although his leg muscles act as a spring, recapturi

ng the energy each time his feet touch down, there’s an average 10% loss with each compression. What must the runner’s additional power output be to account for just this loss, if he averages 0.8 s per stride?
Physics
1 answer:
Darina [25.2K]3 years ago
5 0

Answer: P = 36.75W

The additional power needed to account for the loss is 36.75W.

Explanation:

Given;

Mass of the runner m= 60 kg

Height of the centre of gravity h= 0.5m

Acceleration due to gravity g= 9.8m/s

The potential energy of the body for each step is;

P.E = mgh

P.E = 60 × 9.8 × 0.5

PE = 294J

Since the average loss per compression on the leg is 10%.

Energy loss = 10% (P.E)

E = 10% of 294J

E = 29.4J

To calculate the runner's additional power

given that time per stride is = 0.8s

Power P = Energy/time

P = E/t

P = 29.4J/0.8s

P = 36.75W

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Magnetic field lines come from North pole and goes to south pole, as there are two north poles, they will be going from both the poles.

In short, Your Answer would be Option 4

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3 0
3 years ago
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Six moles of an ideal gas are in a cylinder fitted at one end with a movable piston. The initial temperature of the gas is 28.0
mel-nik [20]

Answer:

63.5 °C

Explanation:

The expression for the calculation of work done is shown below as:

w=P\times \Delta V

Where, P is the pressure

\Delta V is the change in volume

Also,

Considering the ideal gas equation as:-

PV=nRT

where,  

P is the pressure

V is the volume

n is the number of moles

T is the temperature  

R is Gas constant having value = 8.314 J/ K mol

So,

V=\frac{nRT}{P}

Also, for change in volume at constant pressure, the above equation can be written as;-

\Delta V=\frac{nR\times \Delta T}{P}

So, putting in the expression of the work done, we get that:-

w=P\times \frac{nR\times \Delta T}{P}=nR\times \Delta T

Given, initial temperature = 28.0 °C

The conversion of T( °C) to T(K) is shown below:

T(K) = T( °C) + 273.15  

So,  

T₁ = (28.0 + 273.15) K = 301.15 K

W=1770 J

n = 6 moles

So,

1770\ J=6 moles\times 8.314\ J/ Kmol \times (T_2-301.15\ K)

Thus,

T_2=301.15\ K+\frac{1770}{6\times 8.314}\ K

T_2=336.63\ K

The temperature in Celsius = 336.63-273.15 °C = 63.5 °C

<u>The final temperature is:- 63.5 °C</u>

7 0
3 years ago
Direct tension indicators are sometimes used instead of torque wrenches to ensure that a bolt has a prescribed tension when used
natali 33 [55]

Complete Question

The complete question is shown on the uploaded image

Answer:

The tension on the shank is  T =8391.6 N

Explanation:

From the question we are told that

       The strain on the strain on the head is \Delta l = 0.1 mm/mm = \frac{0.1}{1000} = 0.1 *10^{-3} m/m

         The contact area is  A = 2.8 mm^2 = 2.8* (\frac{1}{1000} )^2 = 2.8*10^{-6} m^2  

Looking at the first diagram

           At  600 MPa of stress

               The strain is  0.3mm/mm

          At   450 MPa of stress

                 The strain is   0.0015 mm/mm

 To find the stress at  \Delta l we use the interpolation method

            \frac{\sigma_{\Delta l} -  \sigma_{0.0015} }{ \sigma _ {0.3} - \sigma_{0.0015} } = \frac{e_{\Delta l }  - e_{0.0015}}{e_{0.3} - e_{ 0.0015}}

Substituting values

              \frac{\sigma _{\Delta l} - 450}{600 - 450} = \frac{0.1 -0.0015}{0.3 - 0.0015}

            \sigma _{\Delta l} -450 = 49.50

             \sigma _{\Delta l} = 499.50 MPa

Generally the force on each head is mathematically represented as

              F = \sigma_{\Delta l} * A

Substituting values

             F = 499.50*10^{6} * 2.8*10^{-6}

                =1398.6N

Now the tension on the bolt shank is as a result of the force on the 6 head which is mathematically evaluated as

              T = 6 * F

                  = 6* 1398.6

              T =8391.6 N

                 

     

6 0
3 years ago
Air temperature in a desert can reach 58.0°C (about 136°F). What is the speed of sound (in m/s) in air at that temperature?
Veronika [31]

The approximate speed of sound in dry (0% humidity) air, in meters per second, at temperatures near 0 °C, can be calculated from

c_{air} = (331.3+0.606 \upsilon)

Here

\upsilon = Temperature in Celsius

Replacing with our values we have that

\upsilon=58\° C

c_{air} = (331.3+0.606*58)

c_{air} = 366.1m/s

Therefore the speed of sound in air at that temperature is 366.1m/s

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