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yaroslaw [1]
3 years ago
8

A weightlifter is attempting a biceps curl with a 200 n barbell. the moment arm of the barbell about the elbow joint is 40 cm. t

he moment arm of the elbow flexor muscles is 4 cm. how much force must be produced by these muscles to hold the 200 n barbell in static equilibrium?
Physics
1 answer:
CaHeK987 [17]3 years ago
4 0
Weight of the barbell W = 200 Ndistance of the joint is r = 40 cm = 0.4 mtorque created by the weight at the joint is                  τ = F*r                     = 200 N*0.4 m                     = 80 N.mat equilibrium condition ,    Στ = force*distance - 80 N.m = 0             F'*0.4 - 80 N.m = 0             F'*0.4 = 80          force F' = 200 N
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During which phase of a four stroke engine are waste gases removed?
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3 years ago
The density of aluminum is 2.7 g/cm3. A metal sample has a mass of 52.0 grams and a volume of 17.1 cubic centimeters. Could the
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 Answer:  
__________________________________________________
            No;  the sample could not be aluminum;
since the density of aluminum, " 2.7 g/cm³ " , is NOT close enough to the density of the sample, " 3.04 g/cm³ " .
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Explanation:
________________________________________________
Density is expressed as "mass per unit volume" ;

  in which:
     "mass, "m", is expressed in units of "g" (grams);  and:
     "Volume, "V", is expressed in units of "cm³ " (such as in this problem); or                                                   in units of "mL" ;
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            {Note the exact conversion:  " 1 cm³ = 1 mL " .}. 
__________________________________________________
  The formula for density:  D = m/V ;

Given:  The density of aluminum is:  2.7 g/cm³.

Given:  A sample has a mass of 52.0 g ; and Volume of 17.1 cm³ ; could it be aluminum?
_________________________________________________________
Let us divide the mass of the sample by the volume of the sample;
by using the formula:
___________________________________________
            D = m / V ;  

     and see if the value is at, or very close to "2.7 g/cm³ ".  

If it is, then it could be aluminum.
____________________________________________________
The density for the sample:

  D = (52.0 / 17.1)   g/cm³ = 3.0409356725146199 g/cm³ ;
                                              →round to "3 significant figures" ;
                                          = 3.04 g/cm³ .
_______________________________________________
No; the sample could not be aluminum; since the density of aluminum, 
   "2.7 g/cm³ "   is NOT close enough to the density of the sample,
                        "3.04 g/cm³ " .
____________________________________________________
5 0
3 years ago
An engine draws energy from a hot reservoir with a temperature of 1250 K and exhausts energy into a cold reservoir with a temper
dimulka [17.4K]

Answer:

The power output of this engine is  P =  17.5 W

The  the maximum (Carnot) efficiency is  \eta_c  = 0.7424

The  actual efficiency of this engine is  \eta _a  = 0.46

Explanation:

From the question we are told that

    The temperature of the hot reservoir is  T_h = 1250 \ K

      The temperature of the cold reservoir  is  T_c  =  322 \ K

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substituting values

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    P =  17.5 W

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substituting values

         \eta _a  =  \frac{63000}{1.37*10^{5}}

         \eta _a  = 0.46

     

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