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3 years ago

2 clues about a chemical change

Physics

1 answer:

Evgesh-ka [11]3 years ago

6 0

A change in color, a formation of gas or bubbles, temperature change.

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An underwater scuba diver sees the Sun at an apparent angle of 43.0° above the horizontal. What is the actual elevation angle of

Inessa05 [86]

Answer:

The actual elevation angle is 12.87 degrees

Explanation:

In the attachment you can clearly see the situation. The angle of elevation as seen for the scuba diver is shown in magenta, we conclude that $\theta_2=90-43=47$ .

Using Snell's Law we can write:

$n_1\sin(\theta_1)=n_2\sin(\theta_2)$

$\implies \sin(\theta_1)=\frac{n_2}{n_1}\sin(\theta_2)$ ,

Let's approximate the index of refraction of the air (medium 1 in the picture) to 1.

We thus have:

$\sin(\theta_1)=n_2\sin(\theta_2)=1.333\sin(47)$

$\implies\theta_1=\arcsin[n_2\sin(\theta_2)]=\arcsin[1.333\sin(47)]\approx 77.13$ . Calling $\alpha$ the actual angle of elevation, we get from the picture that $\alpha=90-77.13=12.97$

7 0

3 years ago

An EM wave has a speed of 3 x 10 ^ 8 m/s and a wavelength of 6 x 10 ^ -7 m. What is the frequency of the wave? 90 Hz 180 Hz 2 x

arsen [322]

F = 3x10^8m/s / 6x10^-7m = Hz

5 0

3 years ago

A 20 kg crate initially at rest on a horizontal floor requires a 80 N horizontal force to set it in motion. Find the coefficient

e-lub [12.9K]

Answer:

<em>The coefficient of static friction between the crate and the floor is 0.41</em>

Explanation:

<u>Friction Force</u>

When an object is moving and encounters friction in the air or rough surfaces, it loses acceleration and velocity because the friction force opposes motion.

The friction force when an object is moving on a horizontal surface is calculated by:

$Fr=\mu N$ [1]

Where $\mu$ is the coefficient of static or kinetics friction and N is the normal force.

If no forces other then the weight and the normal are acting upon the y-direction, then the weight and the normal are equal in magnitude:

N = W = m.g

The crate of m=20 Kg has a weight of:

W = 20*9.8

W = 196 N

The normal force is also N=196 N

We can find the coefficient of static friction by solving [1] for $\mu$ :

$\displaystyle \mu=\frac{Fr}{N}$

The friction force is equal to the minimum force required to start moving the object on the floor, thus Fr=80 N and:

$\displaystyle \mu=\frac{80}{196}$

$\mu=0.41$

The coefficient of static friction between the crate and the floor is 0.41

7 0

3 years ago

A paleontologist estimates that when a particular rock formed, it contained 12 mg of the radioactive isotope potassium-40, which

leva [86]

Answer:

$t = 2.52 billion \:years$

Explanation:

As we know by radioactivity law

$N = N_o e^{-\lambda t}$

so here we will have

$N = 3 mg$

$N_o = 12 mg$

now we will have

$3 = 12 e^{-\lambda t}$

$\lambda t = ln 4$

now we also know that

$\lambda = \frac{ln2}{1.26 \times 10^6 yrs}$

$t = 1.26\times 10^6\times \frac{ln4}{ln2}$

$t = 2.52 billion \:years$

7 0

3 years ago

Explain how surface waves can have characteristics of both longitudinal waves and transverse waves. Please use 3 content related

bonufazy [111]

Answer: Search Results

Featured snippet from the web

Answer: Surface waves can have characteristics of both longitudinal and transverse waves in the following way; The motion of the surface waves is up and down which is perpendicular to the direction of the wave. This is similar to the motion of transverse waves whereas the the motion of longitudinal.

Explanation:

7 0

2 years ago