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4 years ago

13

When a plastic rod is rubbed with a wool cloth, the wool acquires a positive charge. What is the best explanation for this effec

t?

1 answer:

Jlenok [28]4 years ago

7 0

Answer:

I suggest you read more on Triboelectric effect

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What part of the Greek model of the atom has been set aside by current scientific knowledge

Elenna [48]

Im pretty sure that the first modle had the atom fully solid with no gaps!

3 0

3 years ago

A physics student stands on a cliff overlooking a lake and decides to throw a softball to her friends in the water below. She th

aliina [53]

Answer:

58.5 m

Explanation:

First of all, we need to find the total time the ball takes to reach the water. This can be done by looking at the vertical motion only.

The initial vertical velocity of the ball is

$u_y = u sin \theta$

where

u = 21.5 m/s is the initial speed

$\theta=33.5^{\circ}$ is the angle

Substituting,

$u_y = (21.5) sin 33.5^{\circ} =11.9 m/s$

The vertical position of the ball at time t is given by

$y = h + u_y t + \frac{1}{2}gt^2$

where

h = 13.5 m is the initial heigth

$g = -9.8 m/s^2$ is the acceleration of gravity (negative sign because it points downward)

The ball reaches the water when y = 0, so

$0 = h + u_yt +\frac{1}{2}gt^2\\0 = 13.5 +11.9 t - 4.9t^2$

Which gives two solutions: t = 3.27 s and t = -0.84 s. We discard the negative solution since it is meaningless.

The horizontal velocity of the ball is

$u_y = u cos \theta = (21.5) cos 33.5^{\circ} =17.9 m/s$

And since the motion along the horizontal direction is a uniform motion, we can find the horizontal distance travelled by the ball as follows:

$d= u_x t = (17.9)(3.27)=58.5 m$

3 0

3 years ago

If an object that weighs 20 N is lifted from the ground to a

Radda [10]

Answer:

false 20 n x 0.32 m = 6.4 J

3 0

4 years ago

Which statement regarding sound traveling in air is correct?

nikdorinn [45]

Answer: D. A wave with a shorter wavelength is always faster than one with a longer wavelength

Explanation: "Imagine two sets of waves that have the same speed. <u><em>If one set has a longer wavelength, it will have a lower frequency (more time between waves). If the other set has a shorter wavelength, it will have a higher frequency</em></u> (less time between waves). Light moves even faster AND has shorter wavelengths."

Why it's not C: "The number of complete wavelengths in a given unit of time is called frequency (f). <em><u>As a wavelength increases in size, its frequency and energy (E) decrease</u></em>. From these equations you may realize that as the frequency increases, the wavelength gets shorter. As the frequency decreases, the wavelength gets longer."

Why it's not B: "The frequency does not change as the sound wave moves from one medium to another. Since the speed changes and the frequency does not, the wavelength must change."

Why it's not A: "Do loud sounds travel faster than soft sounds? No. Both travel at the same speed The speed depends on the medium it passes through. Louder sounds are simply sound waves with higher amplitude traveling at the same speed."

6 0

4 years ago

Cosmic Microwave Background radiation is one piece of supporting evidence for the Big Band Theory. Are these microwaves at the l

dolphi86 [110]

Answer:

it is long.

Explanation:

I know the answer but I don't know how to explain it

3 0

3 years ago