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VLD [36.1K]
4 years ago
8

Assuming a typical efficiency for energy use by the body, how many slices of pizza must you eat to walk for 2.5 h at a speed of

5.0 km/h? Assume that your mass is 68 kg, metabolic power of 68 kg individual walking at 5 km/h is 380 W, and the energy content of slice of pizza is 1260 kJ.
Physics
1 answer:
larisa86 [58]4 years ago
6 0

Answer:

2.7 Pizzas.

Explanation:

The power required to walk through 5km in 1 hour is 380W.

A watt is basically Jules per second, then we need to standardized this measurement to second.

5km/hr is equal to,

\frac{5km}{hr}*\frac{1hr}{3600s}*\frac{1000m}{1km}=1.389m/s

Walking by 2.5 hours is equal to a distance of,

d=v*t=1.389*(2.5*3600) = 12500m

The total energy required then would be,

E = \frac{380J}{1.389m/s}(12500)=3.4199*10^6J

Then we know that one pizza slice gives 1260*10^3J of energy, the total pizza needed are,

\eta = \frac{3.4199*10^6}{1260*10^3} = 2.7142

<em>Then you need to buy 3 pizza.</em>

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Using equations, determine the temperature, pressure and density of the air for a aircraft flying at 19.5 km. Is this aircraft s
Viefleur [7K]

Answer:

a) - 72.5°c

b) pressure = 3625.13 Pa

c) density =  0.063 kg/m^3

d) it is a subsonic aircraft

Explanation:

a) Determine Temperature

Temperature at 19.5 km ( 19500 m )

T = -131 + ( 0.003 * altitude in meters )

  =  -131 + ( 0.003 * 19500 ) = - 72.5°c

b) Determine pressure and density at 19.5 km altitude

Given :

Po (atmospheric pressure at sea level )  = 101kpa

R ( gas constant of air ) = 0.287 KJ/Kgk

T = -72.5°c ≈ 200.5 k

pressure = 3625.13 Pa

hence density = 0.063 kg/m^3

attached below is the remaining part of the solution

C) determine if the aircraft is subsonic or super sonic

Velocity ( v ) = \sqrt{CRT}  =  \sqrt{1.4*287*200.5 } = 283.8 m/s

hence it is a subsonic aircraft

4 0
3 years ago
A racecar driver steps on the gas, and his racecar travels 20 meters in 2 seconds starting from rest. The acceleration of the ra
givi [52]

Answer:

2.5m/s^2

Explanation:

Step one:

given

distance = 20meters

time = 2 seconds

initial velocity u= 0m/s

let us solve for the final velocity

velocity = distance/time

velocity= 20/2

velocity= 10m/s

v^2=u^2+2as\\\\10^2=0^2+2*a*20\\\\100=40a

divide both sides by 40

a= 100/40\\\\a=10/4\\\\a= 5/2\\\\a= 2.5m/s^2

5 0
3 years ago
Help again please !!!
rusak2 [61]
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5 0
3 years ago
Breaking a pencil in half is an example of: options:
Licemer1 [7]

Answer:

b

Explanation:

8 0
3 years ago
Read 2 more answers
The microwaves in a certain microwave oven have a wavelength of 12.2 cm. How wide must this oven be so that it will contain five
leva [86]

Answer:

a

 l = 0.305 \  m

b

  f = 3.0*10^{11} \  Hz

Explanation:

From the question we are told that

  The  wavelength is  \lambda  =  12.2 \  cm  = 0.122 \  m

  The  number of antinodal planes of the electric field considered is n  =  5

The  width is mathematically represented as

       l  =  \frac{ n \lambda}{2}

       l = \frac{5 * 0.122 }{ 2}

      l = 0.305 \  m

Generally the  frequency the errors was made is  mathematically represented as

   f =  \frac{c}{\lamda_k}

Here c is the speed of light with value  c =  3.0*10^{8} \  m/s

     \lambda_k is the wavelength of the microwave has to be in order for there still to be five antinodal planes of the electric field along the width of the oven, which is mathematically represented as

     \lambda_k  =  \frac{ \lambda *  \frac{0.04}{2} }{n/2}

      \lambda_k  =  \frac{0.122*0.02}{5/2}

So

   f =  \frac{3.0*10^{8}}{0.000976}

    f = 3.0*10^{11} \  Hz

   

       

8 0
3 years ago
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