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lianna [129]
2 years ago
10

Rafiq has heard that continued exposure to light for 10 days can change the colour of some blue dyes used to colour cotton cloth

ing. He decides to test this. He takes a piece of clothing dyed with a blue dye which is suspected to lose colour on such exposure. He cuts the cloth into two pieces.
Which experiment is likely to help him conclude if the dye indeed can change colour?
He should expose, for 10 days-

A. Both pieces under 2 identical lamps.
B. One piece under a lamp; keep the other in darkness.
C. One piece for 5 days and one for 10 days under identical lamps
D. One piece folded and one piece spread out under 2 identical lamps.
Physics
1 answer:
Andru [333]2 years ago
4 0
I think the answer is B
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An elaborate pulley consists of four identical balls at the ends of spokes extending out from a rotating drum. A box is connecte
Klio2033 [76]

Answer:

its speed will be less than V

Explanation:

When the ball falls a distance d, its final kinetic energy plus rotational kinetic energy of the drum equals its initial potential energy.

K = U

With its speed V at the end of d, we have

1/2mV² + 1/2Iω² = mgd where I = rotational inertia of drum and balls, ω = angular speed of drum and balls and m = mass of box

1/2mV² + 1/2Iω² = mgd

1/2mV² = mgd - 1/2Iω²

V² = [2(mgd - 1/2Iω²)/m]

V = √[2(mgd - 1/2Iω²)/m]

When the four balls are moved inward closer to the drum, their rotational inertia increases and also its angular speed which thus causes an increase in rotational kinetic energy. But, since the box still falls the same distance of d, its final kinetic energy plus rotational kinetic energy of the drum plus balls still equals its initial potential energy

K = U

I' = new rotational inertia of drum and balls, ω' = new angular speed of drum and balls

With its new speed is now V' at the end of d,

1/2mV'² + 1/2I'ω'² = mgd

1/2mV'² = mgd - 1/2I'ω'²

V² = [2(mgd - 1/2I'ω'²)/m]

V' = √[2(mgd - 1/2I'ω'²)/m]

Since I' and ω' increase, the rotational kinetic energy of the drum and balls (1/2I'ω'²) increases. Thus, the difference (mgd - 1/2I'ω'²) < (mgd - 1/2Iω²) which implies that the kinetic energy of the box decreases. Hence, since its kinetic energy decreases, its speed V' also decreases.

So,  V' < V

So, its speed will be less than V.

3 0
3 years ago
We would be more likely to get an accurate measurement of the distance from Earth to a nearby star if we took the angular measur
NeTakaya

Answer:

6 month interval

Explanation:

The distance to a nearby star in theory is more simple than

one might think! First we must learn about the parallax effect. This is the mechanism our eyes use to perceive things at a distance! When we look at the star from the earth we see it at different angles throughout the earth's movement around the sun similar to how we see when we cover on eye at a time. Modern telescopes and technology can help calculate the angle of the star to the earth with just two measurements (attached photo!) Since we know the distance of the earth from the sun we can use a simple trigonometric function to calculate the distance to the star. The two measurements needed to calculate the angle of the star to the earth caused by parallax (in short angle θ) are shown in the second attached photo.

So using a simple trigonometric function Sin\theta=\frac{r}{d} we can solve for d which is the distance of the earth to the star:

d=\frac{r}{Sin\theta}

In the first attached photo a picture where r is the distance to the star and the base of the triangle is the diameter of the earth.

8 0
3 years ago
Benjamin Franklin has convinced his hapless assistant Mike Piepan to participate in an experiment on electiricty. Ben has set up
ad-work [718]

Answer:

Mike will receive an electric shock

Explanation:

Human body is a conductor of electricity. When lightning strikes rod and give it negative charge, the rod will dissipate its charge as soon as it comes in contact with earth via conduting material. Mike will receive a severe electric shock as negatice charge pass through his body to other rod and to the ground.His body will feel numb. He may also get unconscious.

5 0
3 years ago
When light of frequency equal to 2.40 × 1015 s−1 shines on the surface of silver metal, the kinetic energy of ejected electrons
sesenic [268]

Answer: 9.98 *10^-19 J

Explanation: In order to explain this probelm we have to consider the balance enegy for photoelectric effect.

h*f-W=Ek where h is the Planck constant and W the work function and Ek the kinetic energy. f is the frequency of light.

W=h*f-Ek=6.62*10^-34*2.4*10^15-5.9*10^-19=9.98*10^-19J

3 0
3 years ago
A point charge Q at the center of a sphere of radius R produces an electric flux of Φ coming out of the sphere. If the charge r
Dafna1 [17]

Remains the same

Explanation:

According to Gauss's law, the electric flux through a closed surface is proportional to the charge enclosed by the surface. So no matter how big or small we make the surface that encloses the charge, the electric flux remains the same because it only depends on the enclosed charge, not surface area.

3 0
2 years ago
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