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3 years ago

7

The elastic energy stored in your tendons can contribute up to 35%% of your energy needs when running. Sports scientists find th

at (on average) the knee extensor tendons in sprinters stretch 41 mmmm while those of nonathletes stretch only 33 mmmm . The spring constant of the tendon is the same for both groups, 33 N/mmN/mm. Part A What is the difference in maximum stored energy between the sprinters and the nonathletes

1 answer:

zzz [600]3 years ago

4 0

Answer:

11.16 J

Explanation:

Elastic energy (E) stored in the tendon is given by 1/2ke^2

SPRINTERS

k = 31N/mm = 31N/mm × 1000mm/1m = 31,000N/m

e = 41mm = 41mm × 1m/1000mm = 0.041m

E = 1/2 × 31,000 × 0.041^2 = 26.06J

NON-ATHLETES

k = 31,000N/m

e = 31mm = 31mm × 1m/1000 = 0.031m

E = 1/2 × 31,000 × 0.031^2 = 14.90 J

Difference = 26.06 J - 14.90 J = 11.16 J

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What simple machine can be described as a shaft that is attached to the center of a wheel?

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4 years ago

if pes represents the potential energy stored in a spring in kg•m^2/s^2 and x represents the change in the springs length from i

musickatia [10]

Unit for x - the change in the spring length:
x = [ m ]
PE s = 1/2 k x²
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Answer: The unit for spring constant k is kg/ s²

8 0

3 years ago

The concrete post (Ec = 3.6 × 106 psi and αc = 5.5 × 10-6/°F) is reinforced with six steel bars, each of 78-in. diameter (Es = 2

masha68 [24]

Answer:

the normal stress induced by the concrete post $\sigma_c = 67.26 psi$

the normal stress induced by the steel $\sigma_s = - 1795.84 psi$

Explanation:

Given that:

Modulus for elasticity for concrete post $E_c$ = $3.6 *10^6$ psi

Thermal coefficient for concrete post $\alpha _c$ = $5.5 *10^{-6}/^0F$

Modulus for elasticity of steel bar $E_s$ = $29*10^6psi$

Thermal coefficient of steel bar $\alpha _2$ = $6.5*10^{-6}/^0F$

Change in temperature ΔT = 80°F

Diameter of the steel rood = 7/8-in

Area of the steel rod $A_s$ = $6(\frac{ \pi}{4} )(d_s)^2$

= $6(\frac{ \pi}{4} )(\frac{7}{8} )^2$

= 3.61 in²

Area of concrete parts $A_c$ = (10)(10) - $A_s$

= (100 - 3.61) in²

= 96.39 in²

The total strain developed in the concrete post can be expressed as:

= $[\frac{1}{E_cA_c}+\frac{1}{E_sA_s}]P=(\alpha_s-\alpha_c)(\delta T)$

= $[\frac{1}{(3.6*10^6)(96.39)}+\frac{1}{(29*10^6)(3.61)}]P=(6.5*10^{-6}-5.5*10^{-6})(80)$

= $[(2.88*10^{-9}) +(9.55*10^{-9}]P = 8.0*10^{-5}$

= $1.234*10^{-8}P = 8.0*10^{-5}$

$P = \frac {8.0*10^{-5}}{1.234*10^{-8}}$

P = 6482.98 lb

Since, the normal stress in concrete is induced as a result of temperature rise; we have the expression :

$\sigma_c =\frac{P}{A_c}$

$\sigma_c = \frac{6482.98}{96.39}$

$\sigma_c = 67.26 psi$

Thus, the normal stress induced by the concrete post $\sigma_c = 67.26 psi$

Also; the normal stress in the steel bars induced as a result of temperature rise is as follows:

$\sigma_s = \frac{-P}{A_s}$

$\sigma_s =\frac{-6482.98}{3.61}$

$\sigma_s = - 1795.84 psi$

Thus, the normal stress induced by the steel $\sigma_s = - 1795.84 psi$

6 0

4 years ago

Which is a unit of volume?<br><br> A) centimeter <br> B) meter <br> C) milligram <br> D) milliliter

german

Answer:

I think milligram is the correct answer.

6 0

3 years ago

The correct equation for the x component of a vector named A with an angle measured from the x axis would be which of the follow

Lady_Fox [76]

Answer:

Acosθ

Explanation:

The x-component of a vector is defined as :

Magnitude * cosine of the angle

Maginitude * cosθ

The magnitude is represented as A

Hence, horizontal, x - component of the vector is :

Acosθ

Furthermore,

The y-component is taken as the sin of the of the angle multiplied by the magnitude

Vertical, y component : Asinθ

8 0

3 years ago