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3 years ago

a train is moving at 4.0 km/h. It accelerates at 60 km/h/s for 0.75 h. What is its speed by the of the 0.75 h

Physics

1 answer:

erica [24]3 years ago

8 0

Answer:

49 km/h

Explanation:

60 km/h acceleration for 0.75 hours.

60 × 3/4 = 45 km/h

Take the acceleration and add it to the speed the train was already moving at:

45 + 4 = 49km/h

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A copper wire is stretched so that its length increases and its diameter decreases. what is the result?

Dovator [93]

The result is although the wire's resistivity doesn't change, its resistance does.

Considering the formula for a material's resistance:

R=pL/A

R is directly proportional to L and inversely proportional to A, as can be seen. Be aware that "rho" is a material-specific and intensive attribute (meaning this value will not change if the material is only physically altered). Remember that A = This implies that the relationship between R and the square of r is inverse. When the wire is stretched, the impacts on length are less noticeable than the effects on r. Therefore the wire's resistance increases, but its resistivity stays the same.

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3 years ago

The index of refraction for red light in water is 1.331 and that for blue light is 1.340. A ray of white light enters the water

Alex Ar [27]

Answer:

(a) 47.08°

(b) 47.50°

Explanation:

Angle of incidence = 78.9°

<u>For blue light : </u>

Using Snell's law as:

$\frac {sin\theta_2}{sin\theta_1}=\frac {n_1}{n_2}$

Where,

Θ₁ is the angle of incidence

Θ₂ is the angle of refraction

n₂ is the refractive index for blue light which is 1.340

n₁ is the refractive index of air which is 1

So,

$\frac {sin\theta_2}{sin{78.9}^0}=\frac {1}{1.340}$

${sin\theta_2}=0.7323$

Angle of refraction for blue light = sin⁻¹ 0.7323 = 47.08°.

<u>For red light : </u>

Using Snell's law as:

$\frac {sin\theta_2}{sin\theta_1}=\frac {n_1}{n_2}$

Where,

Θ₁ is the angle of incidence

Θ₂ is the angle of refraction

n₂ is the refractive index for red light which is 1.331

n₁ is the refractive index of air which is 1

So,

$\frac {sin\theta_2}{sin{78.9}^0}=\frac {1}{1.331}$

${sin\theta_2}=0.7373$

Angle of refraction for red light = sin⁻¹ 0.7373 = 47.50°.

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3 years ago

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4 years ago

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You have been working on a new, strong, lightweight ceramic which will be used to replace steel bearing balls. One cubic meter o

marin [14]

Answer:

r=2.6 cm

Explanation:

Hi!

Lets call steel material 1, and the new alloy material 2. You know their densities:

$\rho_1=8.08*10^3\frac{kq}{m^3}\\\rho_2=3.14*10^3\frac{kq}{m^3}$

The volume of a sphere with radius r is given by:

$V=\frac{4}{3}\pi r^3$

Then the masses of the bearings are:

$m_1=\rho_1V_1=\frac{4}{3}\pi r_1^3 \\m_1=\rho_2V_2=\frac{4}{3}\pi r_2^3$

For the masses to be the same:

$\rho_1 V_1 = \rho_2 V_2\\\frac{V_2}{V_1} =\frac{\rho_1}{\rho_2}\\(\frac{r_2}{r_1})^3 = \frac{8.08}{3.14}=2.57\\r_2=\sqrt[3]{2.57}\;r1 =1.37r_1=1.37*1.9cm=2.6cm$

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4 years ago