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Over [174]
3 years ago
5

person is 1.9 m tall. Where should he place the top of a mirror on the wall so he can see the top of his head? Assume his eyes a

re 5.1 cm below the top of his head. Find a minimal vertical distance from the level of the person’s eye
Physics
1 answer:
Helen [10]3 years ago
4 0

Answer:

The minimal vertical distance from the level of the person’s eye is 2.55 cm.

Explanation:

Given;

height of the person = 1.9 m

his eyes are 5.1 cm below the top of his head

If top of his head is the same distance from the mirror as his eyes is from the mirror, then the top of the mirror must be half of his eyes level.

Therefore, the minimal vertical distance from the level of the person’s eye is ¹/₂ x 5.1 cm = 2.55 cm

The minimal vertical distance of the mirror from the level of the person’s eye is 2.55 cm.

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When blue light of wavelength 460 nm falls on a single slit, the first dark bands on either side of center are separated by 45.0
lyudmila [28]

Answer:

width of slit =1.23× 10⁻⁶ m  

Explanation:

we know the condition of diffraction minima,

d sin θ = n λ

λ = wavelength     θ = angle between the central maxima and 1st  minima

d = slit width

for first minima  n = 1

now,

d =\dfrac{n \lambda}{sin \theta}

\theta = \dfrac{45^0}{2} = 22.5^0

d =\dfrac{1\times 460 \times 10^{-9}}{sin 22.5^0}

d = 1228 × 10⁻⁹ m  = 1.228× 10⁻⁶ m

d =  1.23× 10⁻⁶ m

width of slit =1.23× 10⁻⁶ m  

6 0
3 years ago
Lava blown out of a volcano in explosive eruption is called pumice. True False
Ede4ka [16]

The answer is false, pumice is a rock formed from the smoggy powder that shoots out of a volcano called pumicite.


7 0
4 years ago
Read 2 more answers
How old do u have to be to be considered that u died of old age?
Jlenok [28]

Answer:

Average around 75

Explanation:

It's the average age. You don't really always die of old age but it is 75 years of age.

6 0
3 years ago
A 42 N net force is applied to a box which slides horizontally across a floor for 9.0
Rufina [12.5K]

Answer:

The Amount of work is done on the box by the net force is 378 Joules.

Explanation:

Given:

A 42 N net force is applied to a box which slides horizontally across a floor.

Force = 42 N

Force applied for a displacement of 9.0 m

Displacement = 9.0 m

To Find:

Amount of work is done on the box by the net force = ?

i.e Work = ?

Solution:

When a force causes a object to move, work is being done on the object by the force. Work is the measure of energy transfer when a force (F) moves an object through a distance (d).

Formula is given by

Work=Force\times Displacement

Substituting the given values we get

∴ Work = 42 × 9.0

∴ Work = 378 N-m

or

∴ Work = 378 Joules

The Amount of work is done on the box by the net force is 378 Joules.

8 0
4 years ago
A horizontal pipe 18.0 cm in diameter has a smooth reduction to a pipe 9.00 cm in diameter. If the pressure of the water in the
Rzqust [24]

Answer:

The rate of flow of water is 71.28 kg/s

Solution:

As per the question:

Diameter, d = 18.0 cm

Diameter, d' = 9.0 cm

Pressure in larger pipe, P = 9.40\times 10^{4}\ Pa

Pressure in the smaller pipe, P' = 2.80\times 10^{4}\ Pa

Now,

To calculate the rate of flow of water:

We know that:

Av = A'v'

where

A = Cross sectional area of larger pipe

A' = Cross sectional area of larger pipe

v = velocity of water in larger pipe

v' = velocity of water in larger pipe

Thus

\pi \frac{d^{2}}{4}v = \pi \frac{d'^{2}}{4}v'

18^{2}v = 9^v'

v' = 4v

Now,

By using Bernoulli's eqn:

P + \frac{1}{2}\rho v^{2} + \rho gh = P' + \frac{1}{2}\rho v'^{2} + \rho gh'

where

h = h'

\rho = 10^{3}\ kg/m^{3}

9.40\times 10^{4} + \frac{1}{2}\rho v^{2} = 2.80\times 10^{4} + \frac{1}{2}\rho (4v)^{2}

6.6\times 10^{4}  = \frac{1}{2}\rho 15v^{2}

v = \sqrt{\frac{2\times 6.6\times 10^{4}}{15\times 10^{3}}} = 8.8\ m/s

Now, the rate of flow is given by:

\frac{dm}{dt} = \frac{d}{dt}\rho Al = \rho Av

\frac{dm}{dt} = 10^{3}\times \pi (\frac{18}{2}\times 10^{- 2})^{2}\times 8.8 = 71.28\ kg/s

3 0
3 years ago
Read 2 more answers
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