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Pavlova-9 [17]
3 years ago
8

a skinny girl devours food that is equivalent to 600 kcal, as she is anorexic she repents and wants to lose twice as many calori

es by lifting 20 kg weights to a height of 1.9 m. If she measures 1.7m ... she calculates the number of times she must lift the weights to lose the same amount of energy that she acquired with food and the time she must be exercising if it takes 2 seconds for repetition.
Physics
1 answer:
blondinia [14]3 years ago
4 0

Answer:

Explanation:

Work done in lifting the weight once = mgh

= 20 x 9.8 x (1.9+1.7)

= 705.6 J  

= 705.6 / 4.2 calorie

= 168 cals

Total energy to be spent = 600 x 10³ cals

No of times weight is required to be lifted

= 600 x 10³ / 168

= 3.57  x 10³ times

Total time to be taken = 2 x 3.57 x 10³

= 7.14 x 10³ s

=119 minutes .

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Even in the most advanced circuits, we cannot oscillate electrons back and forth at that rate through wires. But we can oscillat
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Answer:

the oscillations of the electrons must be in the 10⁸ Hz = 100 MHz range

Explanation:

The speed of a wave of radio, television, light, heat, all are manifestations of electromagnetic waves that are oscillations of electric and magnetic fields that support each other, the speed of all these waves is the same and the vacuum is equal to c = 3 108 m / s

All waves have a relationship between the speed of the wave, its frequency and wavelength

          c = λ f

          f = c /λ

for this case lam = 1 m

          f = 3 10⁸/1

          f = 3 10⁸ Hz

the oscillations of the electrons must be in the MHz range

It should be clarified that the speed of light in air is a little lower

          n = c / v

          v = c / n

the refractive index of vacuum is n = 1 and the refractive index of air is n = 1.000002

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3 years ago
How is work related to potential energy and kinetic energy?
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About how long does it take for sound to travel 1 Km?
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Read 2 more answers
A fireman standing on a 15 m high ladder operates a water hose with a round nozzle of diameter 2.02 inch. The lower end of the h
Nataly_w [17]

Answer:

v₁ = 1,606 10⁴ m / s

Explanation:

For this exercise we must use Bernoulli's equation, let's use index 1 for the nozzle on the stairs and index 2 the pump on the street

              P₁ + ½ ρ v₁² + ρ g y₁ = P₂ + ½ ρ v₂² +ρ g y₂

             

The pressure when the water comes out is the atmospheric pressure

           P₁ = P_atm

The difference in height between the street and the nozzle on the stairs is

           y₂-y₁ = 15 m

Now let's use the continuity equation

             v₁ A₁ = v₂ A₁

The area of ​​a circle is

             A = π r² = π (d/2)²

            v₁ π d₁²/ 4 = v₂ π d₂²/ 4

            v₂ = v₁ d₁² / d₂²

Let's replace

           P₂-P_atm + ½ ρ [ (v₁ d₁² / d₂²)²- v₁² ] + ρ g (y2-y1) = 0

           P₂- P_Atm + ρ g (y₂-y₁) = ½ ρ v₁² [1- (d₁/d₂)⁴]

           v₁² [1- (d₁/d₂)⁴] = (P₂-P_atm) ρ / 2 + g (y₂-y₁) / 2

Let's reduce the magnitudes to the SI system

           d₂ = 3.37 in (2.54 10⁻² m / 1 in) = 8.56 10⁻² m

           d₁ = 2.02 in = 5.13 10⁻² m

Let's calculate

            v₁² [1- (5.13 / 8.56) 4] = 449.538 10³ 10³/2  -9.8 15/2

            v₁² [0.8710] = 2.2477 10⁸ - 73.5 = 2.2477 10⁸

            v₁ = √ 2.2477 10⁸ /0.8710

             v₁ = 1,606 10⁴ m / s

4 0
3 years ago
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