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Studentka2010 [4]

3 years ago

14

How many helium-filled balloons would it take to lift a person? Assume the person has a mass of 76 kg and that each helium-fille

d balloon is spherical with a diameter of 35 cm .

1 answer:

sergij07 [2.7K]3 years ago

7 0

Answer:

15200 i think im not 100% sure but i tried doing the math

Explanation:

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Describe what a hydrogen bond is. 6th grade answer

r-ruslan [8.4K]

Answer:

<em>Hydrogen bond is the attractive force between the hydrogen attached electronegative atom </em>

Explanation:

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2 years ago

There are no current plans for returning to the moon. <br> True<br> False

inysia [295]

True that’s my answer

8 0

3 years ago

Read 2 more answers

Rod AB has a diameter of 200mm and rod BC has a diameter of 150mm. Find the required temperature increase to close the gap at C.

Leni [432]

Answer:

$T&=\frac{\sigma_{AB}+\sigma_{BC}}{2\alpha E}$

Explanation:

The given data :-

Diameter of rod AB ( d₁ ) = 200 mm.

Diameter of rod BC ( d₂ ) = 150 mm.

The linear co-efficient of thermal expansion of copper ( ∝ ) = 1.6 × 10⁻⁶ /°C

The young's modulus of elasticity of copper ( E ) = 120 GPa = 120 × 10³ MPa.
Consider the required temperature increase to close the gap at C = T °C
Consider the change in length of the rod = бL

Solution :-

$\begin{aligned}\sum H& =0\\-R_A+R_C&=0\\R_A&=R_C\\R_A&=R\\R_C&=R\\R_{A}&=\text{reaction\:force\:at\:A}\\R_{C}&=\text{reaction\:force\:at\:C}\\\sigma_{AB}&=\text{axial\:stress\:at\:A}\\\sigma_{BC}&=\text{axial\:stress\:at\:B}\\\sigma_{AB}&=\frac{R}{A_{A}}\\&=\frac{R_{A}}{A_{A}}\\\sigma_{BC}&=\frac{R_{B}}{A_{B}}\\&=\frac{R}{A_{B}}\\\frac{\sigma_{AB}}{\sigma_{BC}}&=\frac{A_{B}}{A_{B}}\\&=\frac{\frac{\pi}{4}\cdot 150^{2}}{\frac{\pi}{4}\cdot 200^{2}}\\&=\frac{9}{16}\end{aligned}$

$\begin{aligned}\delta L&= (\delta L _{thermal} +\delta L_{axial})_{AB} + ( \delta L _{thermal} +\delta L_{axial})_{BC}\\0& = (\delta L _{thermal} +\delta L_{axial})_{AB} + ( \delta L _{thermal} +\delta L_{axial})_{BC}\\&=\left[\alpha\:T\:L+\left(\frac{-RL}{AE}\right)\right]_{AB}+\left[\alpha\:T\:L+\left(\frac{-RL}{AE}\right)\right]_{BC}\\&=2\:\alpha\:T\:L-\frac{L}{E}(\sigma_{AB}+\sigma_{BC})\\T&=\frac{\sigma_{AB}+\sigma_{BC}}{2\alpha E}\end{aligned}$

5 0

3 years ago

You send a beam of light from a material with index of refraction 1.21 into an unknown material. In order to help identify this

White raven [17]

Answer:

refractive index of the unknown material is 1.33.

Explanation:

μ₁ = 1.21

incidence angle (i) = 41.9°

refraction angle (r) = 37.3°

Let us assume μ be the refractive index of the unknown material

according to snell's law of refraction.

μ₁ sin i = μ₂ sin r

1.21 × sin 41.9° = μ × sin 37.3°

μ = 1.33

hence the refractive index of the unknown material comes out top be 1.33

6 0

3 years ago

Which description correctly summarizes how an electric motor causes an axle to turn?

alexira [117]

Answer:

B on edge

Explanation:

the piles of the magnetic field generated around the armature are attracted to the opposite poles of the permanent magnent. As the opposite poles align, the commutator reverses the current direction so like poles are aligned and the armature continues to spin

6 0

3 years ago