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nekit [7.7K]
3 years ago
10

A small mirror is attached to a vertical wall, and it hangs a distance of 1.87 m above the floor. The mirror is facing due east,

and a ray of sunlight strikes the mirror early in the morning and then again later in the morning. The incident and reflected rays lie in a plane that is perpendicular to both the wall and the floor. Early in the morning, the reflected ray strikes the floor at a distance of 3.56 m from the base of the wall. Later on in the morning, the ray is observed to strike the floor at a distance of 1.46 m from the wall. The earth rotates at a rate of 15.0o per hour. How much time (in hours) has elapsed between the two observations
Physics
1 answer:
Oksana_A [137]3 years ago
4 0

Answer:

 t = 1.62 h

Explanation:

A flat mirror fulfills the law of reflection where the incident angle is equal to the reflected angle.

          θ_i = θ_r

If we use trigonometry to find the angles, the mirror is at a height of L = 1.87 m,   and the reflected rays reach a distance x1 = 3.56 m

         tan θ₁ = x₁ / L

         tan θ₁ = \frac{3.56}{1.87}

         θ₁ = tan⁻¹  1.90

         θ₁ = 62.29º

for the second case x₂ = 1.46 m

        tan θ₂ = x₂ / L

        θ₂ = tan⁻¹  \frac{1.46}{1.87}

        θ₂ = 37.98º

the difference in degree traveled is

         Δθ = θ₁- θ₂

          Δθ = 62.29 - 37.98

          Δθ = 24.31º

as in the exercise they indicate that every 15º there is an hour

         t = 24.31º (1h / 15º)

         t = 1.62 h

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An air hockey game has a puck of mass 30 grams and a diameter of 100 mm. The air film under the puck is 0.1 mm thick. Calculate
OverLord2011 [107]

Answer:

time required after impact for a puck is 2.18 seconds

Explanation:

given data

mass = 30 g = 0.03 kg

diameter = 100 mm = 0.1 m

thick = 0.1 mm = 1 ×10^{-4} m

dynamic viscosity = 1.75 ×10^{-5} Ns/m²

air temperature = 15°C

to find out

time required after impact for a puck to lose 10%

solution

we know velocity varies here 0 to v

we consider here initial velocity = v

so final velocity = 0.9v

so change in velocity is du = v

and clearance dy = h

and shear stress acting on surface is here express as

= µ \frac{du}{dy}

so

= µ  \frac{v}{h}   ............1

put here value

= 1.75×10^{-5} × \frac{v}{10^{-4}}

= 0.175 v

and

area between air and puck is given by

Area = \frac{\pi }{4} d^{2}

area  =  \frac{\pi }{4} 0.1^{2}

area = 7.85 × \frac{v}{10^{-3}} m²

so

force on puck is express as

Force = × area

force = 0.175 v × 7.85 × 10^{-3}

force = 1.374 × 10^{-3} v    

and now apply newton second law

force = mass × acceleration

- force = mass \frac{dv}{dt}

- 1.374 × 10^{-3} v = 0.03 \frac{0.9v - v }{t}

t =  \frac{0.1 v * 0.03}{1.37*10^{-3} v}

time = 2.18

so time required after impact for a puck is 2.18 seconds

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3 years ago
SO MANY POINTS! WILL MARK BRAINIEST!!!! PLZ BE FASSTT!
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Explanation:

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Answer: - 452.088joule

Explanation:

Given the following :

Mass of water = 12g

Change in temperature(Dt) = (11 - 20)°C = - 9°C

Specific heats capacity of water(c) = 4.186j/g°C

Q = mcDt

Where Q = quantity of heat

Q = 12g × 4.186j/g°C × - 9°C

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Normally, jet engines push air out the back of the engine, resulting in forward thrust, but commercial aircraft often have thrus
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Answer:

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Thrust reversal is also known as reverse thrust. It acts opposite to the motion of the aircraft by providing the deceleration.

Commercial aircraft moves the ejected air in the forward direction means that the thrust will acts opposite to the motion of the aircraft that is backward direction due to thrust reversal. This thrust force might be used to decelerate the craft.

Uses of thrust reversal in practice:

When the ejected air is moving forward direction then the thrust force moving backward direction due to reversal thrust the speed of the craft slows down.

When the ejected air is moving in the downward direction then the thrust force acts in the upward direction, due to reversal thrust, the jets can take off vertically without needing a runway this way.

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3.00 m3 of a fixed mass of a gas at 150 kPa. Calculate the pressure if the volume is reduced to 1.20 m3 at a constant temperatur
viktelen [127]

Answer:

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Explanation:

Given that,

Initial volume, V₁ = 3 m³

Initial pressure, P₁ = 150 kPa

Final volume, V₂ = 1.2 m³

We need to find the final pressure.

At constant temperature,

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So, the new pressure is 375 kPa.

6 0
3 years ago
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