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galina1969 [7]
3 years ago
9

A lamp is 10% efficient.How much electrical energy must be supplied to the lamp each second if it produces 20 J of light energy

per second?
Physics
1 answer:
k0ka [10]3 years ago
6 0

If it produces 20J of light energy in a second, then that 20J is the 10% of the supply that becomes useful output.

20 J/s = 10% of Supply

20 J/s = (0.1) x (Supply)

Divide each side by 0.1:

Supply = (20 J/s) / (0.1)

<em>Supply = 200 J/s  </em>(200 watts)

========================

Here's something to think about:  What could you do to make the lamp more efficient ?  Answer:  Use it for a heater !

If you use it for a heater, then the HEAT is the 'useful' part, and the light is the part that you really don't care about.  Suddenly ... bada-boom ... the lamp is 90% efficient !

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What evidence can you cite to support the claim that the frequency of light does not change upon reflection?
sergiy2304 [10]

Answer: The color of an image is identical to the color of the object forming the image. When you look at yourself in a mirror, the color of your eyes doesn’t change. The fact that the color is the same is evidence that the frequency of light doesn’t change upon reflection. 2.

Hope this helps!!

5 0
3 years ago
Why is it important to use the correct number of significant digits when
Artemon [7]

Answer:

D

Explanation:

Scientists use significant figures to avoid claiming more accuracy in a calculation than they actually know.

6 0
3 years ago
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A string attached to an airborne kite was maintained at an angle of 40.0 with the ground. if 120m of string was reeled in to ret
AleksAgata [21]
The hypotenuse is measured at 120 meters of string, and you need to solve for the leg of the triangle that is horizontal. The degree is 40, so use trigonometry to figure it out. 
Cosin (40) is equal to around .766 
Adjacent/Hypotenuse 
x/120 = cos40 
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5 0
3 years ago
a 1500 kg car traveling at 15 m/s to the south collides with a 4500 kg truck that is intially at rest at a spotlight. The car an
harkovskaia [24]

Answer:

3.75 m/s south

Explanation:

Momentum before collision = momentum after collision

m₁ u₁ + m₂ u₂ = m₁ v₁ + m₂ v₂

Since the car and truck stick together, v₁ = v₂.

m₁ u₁ + m₂ u₂ = (m₁ + m₂) v

Given m₁ = 1500 kg, u₁ = -15 m/s, m₂ = 4500 kg, and u₂ = 0 m/s:

(1500 kg) (-15 m/s) + (4500 kg) (0 m/s) = (1500 kg + 4500 kg) v

-22500 kg m/s = 6000 kg v

v = -3.75 m/s

The final velocity is 3.75 m/s to the south.

4 0
3 years ago
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1. he traveled a total of 24 miles
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