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Stolb23 [73]
3 years ago
11

At what distance will a 80 W lightbulb have the same apparent brightness as a 120 W bulb viewed from a distance of 40 m

Physics
1 answer:
liq [111]3 years ago
4 0

Answer:

32.6mm

Explanation:

Using area of a sphere(bulb) = 4πr²

So A is proportional to radius²

So the Energy will be proportional to r²

But 120/80 = 1.5 is the energy factor so

Using

1.5/d² = 1/r²

1.5/40²= 1/r^2

r = √( 40²/ 1.5)

r = 32.6m

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A uniform beam resting on two pivots has a length L = 6.00 m and weight M = 220 lbs. The pivot under the left end exerts a norma
gulaghasi [49]

Answer:

x = 4,138 m

Explanation:

For this exercise, let's use the rotational equilibrium equation.

Let's fix our frame of reference on the left side of the pivot, the positive direction for anti-clockwise rotation

         ∑ τ = 0

         n₁ 0 - W L / 2 + n₂ 4 - W_woman  x = 0

         x = (- W L / 2 + 4n2) / W_woman

Let's reduce the magnitudes to the SI System

         M = 6 lbs (1 kg / 2.2 lb) = 2.72 kg

         M_woman = 130 lbs = 59.09 kg

Let's write the transnational equilibrium equation

         n₁ + n₂ - W - W_woman = 0

         n₁ + n₂ = W + W_woman

        n₁ + n₂ = (2.72 + 59.09) 9.8

At the point where the system begins to rotate, pivot 1 has no force on it, so its relation must be zero (n₁ = 0)

          n₂ = 605,738 N

 

Let's calculate

         x = (-2.72 9.8 6/2 + 4 605.738) / 59.09 9.8

         x = 4,138 m

4 0
3 years ago
Rank these electromagnetic waves on the basisof their speed (in vacuum). Rank from fastest to slowest. To rank items as equivale
adelina 88 [10]

Answer: On the basis of speed they are all equivalent.

Yellow light = Fm radio wave = Green light = X-ray = AM radio wave = Infrared wave

Explanation:

Yellow light, Fm radio wave, Green light ,X-ray, AM radio wave and Infrared wave are all electromagnetic waves, and all electromagnetic waves move at the same vacuum speed which is the speed of light and is approximately 3.0x10^8 m/s.

They only differ in wavelength and frequency

c = λf

c (speed of light) = λ (wavelength) x f (frequency)

Therefore; on the basis of speed they are all equivalent.

Yellow light = Fm radio wave = Green light = X-ray = AM radio wave = Infrared wave

6 0
3 years ago
How long does it take an automobile traveling 66.7 km/h to become even with a car that is traveling in another lane at 52.7 km/h
tresset_1 [31]

Answer:

The  time taken is  t =  32.5 \  s

Explanation:

From the question we are told that

   The  speed  of  first car is  v_1  =  66.7 \ km/h  =  18.3 \  m/s

    The  speed  of  second car is v_2  =  52.7 \ km/h  =  14.64 \  m/s

   The  initial distance of separation is  d =  119 \ m

The distance covered by first car is mathematically represented as

     d_t =  d_i  +  d_f

Here  d_i is the initial distance which is  0 m/s

  and  d_f  is the final distance covered which is  evaluated as d_f  =  v_1 * t

So

     d_t =  0 \  m/s  +  (v_1 * t )

     d_t =  0 \  m/s  +  (18.3 * t )

The distance covered by second  car is mathematically represented as

     d_t =  d_i  +  d_f

Here  d_i is the initial distance which is  119 m

  and  d_f  is the final distance covered which is  evaluated as d_f  =  v_2* t

       d_t =  119  + 14.64 *  t

Given that the two car are now in the same position we have that

    119  + 14.64 *  t  =   0   +  (18.3 * t )

   t =  32.5 \  s

6 0
3 years ago
Sam drives her scooter 7 kilometres north. She stops for lunch and then drives
Talja [164]

Answer:

1. Distance travelled = 12 km.

2. Displacement = 8.6 km

Explanation:

From the question given above, the following data were obtained:

Distance 1 (d₁) = 7 km

Distance 2 (d₂) = 5 km

Total distance =?

Displacement =?

1. Determination of the distance travelled.

Distance 1 (d₁) = 7 km

Distance 2 (d₂) = 5 km

Total distance (dₜ) =?

dₜ = d₁ + d₂

dₜ = 7 + 5

dₜ = 12 km

2. Determination of the displacement.

In the attached photo, R is the displacement.

We can obtain the value of R by using the pythagoras theory as illustrated below:

R² = 7² + 5²

R² = 49 + 25

R² = 74

Take the square root of both side

R = √74

R = 8.6 km

8 0
3 years ago
A thin aluminum rod lies along the x-axis and has current of I = 16.0 A running through it in the +x-direction. The rod is in th
coldgirl [10]

Answer:

a) The magnitude of the magnetic field = 7.1 mT

b) The direction of the magnetic field is the +z direction.

Explanation:

The force, F on a current carrying wire of current I, and length, L, that passes through a magnetic field B at an angle θ to the flow of current is given by

F = (B)(I)(L) sin θ

F/L = (B)(I) sin θ

For this question,

(F/L) = 0.113 N/m

B = ?

I = 16.0 A

θ = 90°

0.113 = B × 16 × sin 90°

B = 0.113/16 = 0.0071 T = 7.1 mT

b) The direction of the magnetic field will be found using the right hand rule.

The right hand rule uses the first three fingers on the right hand (the thumb, the pointing finger and the middle finger) and it predicts correctly that for current carrying wires, the thumb is in the direction the wire is pushed (direction of the force; -y direction), the pointing finger is in the direction the current is flowing (+x direction), and the middle finger is in the direction of the magnetic field (hence, +z direction).

3 0
4 years ago
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