Which of these is an example of a physical change? Question options: wood decaying iron melting paper burning steel rusting

Can someone help me with these questions plz

Korolek [52]

Im not 100% on these but i can try

1. A compound is made up of elements and their different atoms

2.

A. salt- compound (NaCl) is two elements Na (sodium) and Cl (chloride?)

B. Nitrogen- element its on the periodic table

C. Helium- element its on the periodic table

D. Water- compound (H2O) two elements hydrogen and oxygen

3. element, compound, compound, element

Hope this helps

8 0

3 years ago

Do you think there is water on exoplanets

Ksivusya [100]

Answer:

Explanation:

Some exoplanets may depending on the climate and vicinity from the sun.

8 0

3 years ago

Lagrangian mechanics. Determine the equations of motion for a particle of mass m constrained to move on the surface of a cone in

maria [59]

Answer:

Explanation:

Hi!

In order to obtain the Lagrangian of the system we must first write the Kinetic and Potential Energies. Lets orient our axes such that the axis of the cone coincide with the z axis. In cilindrical coordinates we have

$v^{2} = \frac{dr}{dt}^{2} +r^{2} \frac{d\theta }{dt} ^{2} +\frac{dz}{dt} ^{2}$ - (1)

But, since the particle is constrained to move on the surface of the cilinder, we have the following relation between r and z:

$\frac{r}{z}=tan(45)$

or:

$z = r cot(45)$ - (2)

and:

$\frac{dz}{dt} = \frac{dr}{dt} cot(45)$

replacing (2) in (1) we obtain:

$v^{2} = \frac{dr}{dt}^{2} (1+cot(45))+r^{2}\frac{d\theta }{dt} ^{2}$ - (3)

Now the kinetic energy is given as:

$T = \frac{1}{2}m(\frac{dr}{dt}^{2} (1+cot(45))+r^{2}\frac{d\theta }{dt} ^{2})$ - (4)

And the potential energy is given by:

$V = -mgz = -mgr cot(45)$

So the Langrangian is given by:

$L = T - V= \frac{1}{2}m(\frac{dr}{dt}^{2}(1+cot(45)+r^{2})\frac{d\theta }{dt} ^{2}) + mgr cot(45)$

And the equations of motion are:

For θ

$\frac{d}{dt} (mr\frac{d\theta}{dt}) = 0-->mr{d\theta}{dt}=c$

For r

$\frac{d}{dt}(m\frac{dr}{dt}(1+cot(45) )= mgcot(45)+mr\frac{d\theta}{dt} ^{2}\\m\frac{d^{2} r}{dt^{2} }(1+cot(45)= mgcot(45)+mr\frac{d\theta}{dt} ^{2}$

Obtained from the Euler-Langrange equations

Here the conserved quantity is given by the first equation of motion, namely:

$mr\frac{d\theta}{dt}=c$

Which is the magnitude of the angular momentum

7 0

3 years ago

Consider a satellite in a circular orbit around the Earth. If it were at an altitude equal to twice the radius of the Earth, 2RE

Elenna [48]

Answer:

$v=\sqrt{\frac{gR_E}{2}}$

Explanation:

Satellites experiment a force given by Newton's Gravitation Law:

$F=\frac{GMm}{r^2}$

where M is Earth's mass, m the satellite's mass, r the distance between their gravitational centers and G the gravitational constant.

We also know from Newton's 2nd Law that F=ma, so putting both together we will have:

$ma=\frac{GMm}{r^2}$

$a=\frac{GM}{r^2}$

If we are on the surface of the Earth, the acceleration would be g and $r=R_E$ (Earth's radius):

$g=\frac{GM}{R_E^2}$

Which we will write as:

$gR_E^2=GM$

If we are on orbit the acceleration is centripetal ( $a=\frac{v^2}{r}$ ), so we have:

$\frac{v^2}{r}=a=\frac{GM}{r^2}=\frac{gR_E^2}{r^2}$

$v^2=\frac{gR_E^2}{r}$

$v=\sqrt{\frac{gR_E^2}{r}}$

And if this orbit has a radius $r=2R_E$ we have:

$v=\sqrt{\frac{gR_E^2}{2R_E}}=\sqrt{\frac{gR_E}{2}}$

3 0

3 years ago

Read 2 more answers

The differential distribution of ions across the cell membrane is due to the:

DIA [1.3K]

The differential distribution of ions across the cell membrane is due to the "resting membrane potential".

Option: C

Explanation:

The unequal allocation of charged particles like ions between the internal and external portion of cell, and by the varying membrane permeability to various ion forms, understood as resting membrane potential.

Within a sleeping brain, Na+ and K+ ions exhibit concentration gradients throughout the membrane, which push their gradients down through channels, resulting in a differentiation of the charges that generates the resting potential. With K+ than Na+ ions, the membrane is even more permeable, so the resting potential is similar to potassium ion's equilibrium potential.

8 0

3 years ago