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3 years ago

Melting, freezing, and boiling are______ changes

Physics

2 answers:

avanturin [10]3 years ago

6 0

Melting, boiling, and freezing are state changes!
Hope this helps! Any questions please just ask! Thank you so much!

Sever21 [200]3 years ago

5 0

Answer:

Its phase

Explanation:

i just took the test

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True or false materials that are poor conductors are poor insulaters

prohojiy [21]

False, rubber is a poor conductor but is a good insulator.

8 0

3 years ago

Read 2 more answers

A firewoman dropped a person onto the safety net. Right before the person hit the net he had a

sergejj [24]

Answer:

The Mass of a person is calculated to be 28.6kg .

Explanation:

This is based on Kinetic energy and we know, that Kinetic energy is the energy possessed by body by virtue of its motion .

It can be calculated by expression :

K.E=1/2mv²

Velocity of a person = 11.2m/sec

Kinetic energy = 1800J

Mass of person = ?

We know ,

K.E=1/2mv²

so, putting values we have :

1800=1/2 x m x (11.2)²

That is ,

m=1800 x 2 /11.2 x 11.2

m=3600/125.44

m = 28.6 kg

6 0

3 years ago

A train can speed up at a uniform rate of 0.15 m/s2. In what minimum distance can

goblinko [34]

Answer:

d = 2083.33 m

Explanation:

Given that,

Acceleration of the train, a = 0.15 m/s²

The initial speed of the car, u = 0\

Final velocity, v = 25 m/s

We need to find the minimum distance covered by the train. Let it is d. Using third equation of kinematics as follows :

$v^2-u^2=2ad\\\\d=\dfrac{v^2-u^2}{2a}\\\\d=\dfrac{(25)^2-0}{2\times 0.15}\\\\d=2083.33\ m$

So, the minimum distance is 2083.33 m

3 0

3 years ago

When an excited electron falls from n = 3 to n = 2, a red radiation in the Balmer series emitted. What is the frequency of this

vichka [17]

Answer:

The frequency of this photon is $4.57\times10^{14}\ Hz$

(D) is correct option.

Explanation:

Given that,

Excited states,

$n=3$

$n=2$

We need to calculate the wavelength

Using formula for energy

$E=13.6(\dfrac{1}{n^2}-\dfrac{1}{m^2})$

$E=13.6(\dfrac{1}{4}-\dfrac{1}{9})$

$E=1.888\ eV$

$E=1.888\times1.6\times10^{-19}\ J$

$E=3.0208\times10^{-19}\ J$

We need to calculate the frequency

Using formula of frequency

$E=hf$

$f=\dfrac{E}{h}$

Where, E =energy

$f=\dfrac{3.0208\times10^{-19}}{6.63\times10^{-34}}$

$f=4.57\times10^{14}\ Hz$

Hence, The frequency of this photon is $4.57\times10^{14}\ Hz$

4 0

3 years ago

A 20-kg sled is being pulled along the horizontal snow-covered ground by a horizontal force of 26 n. starting from rest, the sle

Vesna [10]

Good morning.

We calculate the acceleration with the <em>Torricelli equation</em>:

$\star\ \boxed{\mathsf{V^2 = V_0^2 + 2a\Delta S}}$

We see that:

$\begin{cases}\mathsf{V_0 = 0}\\\mathsf{V = 2.3 \ m/s}\\\mathsf{\Delta S = 8.9 \ m}\end{cases}$

Now:

$\mathsf{(2.3)^2 = 0^2 + 2a\cdot 8.9}\\ \\ \mathsf{5.29 = 17.8a}\\ \\ \bold{\mathsf{a = 0.3 \ m/s^2}}$

Now we can calculate the resultant force that makes that acceleration of 0.3 m/s² with the 2nd Law of Newton:

$\mathsf{F_r = m\cdot a}\\ \\ \mathsf{F_r = 20\cdot 0.3}\\ \\ \mathsf{F_r = 6 \ N}$

We have a force of 26 N → and a friction force F ←. Adding those vectors, he have a force 6 N →. Therefore:

26 - F = 6

F = 20 N

We have a friction force of 20 N. We calculate the kinect coefficient with the formula:

$\star \ \boxed{\mathsf{F = \mu_k N}}$

Since we are in a horizontal plane, we hava that N = P = mg = 200 N

Therefore:

$\mathsf{20 = \mu_k 200}\\ \\ \boxed{\boxed{\mathsf{\mu_k = 0.1}}}$

5 0

3 years ago