All categories

3 years ago

Which of the following is the best definition of an element?

Physics

1 answer:

Ostrovityanka [42]3 years ago

8 0

Answer:

A. chemical substance whose atoms all have the same number of protons

Explanation:

An element is a substance which contains identical atoms that have the same number of protons in the nucleus.

Elements are arranged in the periodic table according to their atomic number (= number of protons): so atoms of different elements have a different number of protons in their nuclei.

For a neutral atom, the number of electrons around the nucleus is also equal to the number of protons.

Moreover, atoms of the same element can have a different number of neutrons, despite having the same number of protons - these atoms are called isotopes.

You might be interested in

During light activity, a 70-kg person may generate 200 kcal

Lerok [7]

Answer:

$2.75387\ ^{\circ}$

Explanation:

m = Mass of person = 70 kg

c = Specific heat of human body = $0.83\ J/kg^{\circ}C$

$\Delta T$ = Change in temperature

Time taken is 1 hour

Heat is given by

$Q=mc\Delta T\\\Rightarrow \Delta T=\dfrac{Q}{mc}\\\Rightarrow \Delta T=\dfrac{0.8\times 200\times 1}{70\times 0.83}\\\Rightarrow \Delta T=2.75387\ ^{\circ}C$

The rise in temperature is $2.75387\ ^{\circ}C$

3 0

3 years ago

Explain why, if you go to the moon, your weight would change but your mass wouldnt

Evgen [1.6K]

There's little gravity so your weight would change but not your mass

3 0

3 years ago

Equation of motion description is v=20+2t.How big is the initial speed,acceleration?

trasher [3.6K]

Answer:

the initial velocity is 20 m/s and the acceleration is 2 m/s²

Explanation:

Given equation of motion, v = 20 + 2t

If V represents the final velocity of the object, then the initial velocity and acceleration of the object is calculated as follows;

From first kinematic equation;

v = u + at

where;

v is the final velocity

u is the initial velocity

a is the acceleration

t is time of motion

If we compare (v = u + at) to (v = 20 + 2t)

then, u = 20 and

a = 2

Therefore, the initial velocity is 20 m/s and the acceleration is 2 m/s²

4 0

3 years ago

A solenoid 25.0 cmcm long and with a cross-sectional area of 0.550 cm^2 contains 460 turns of wire and carries a current of 90.0

ankoles [38]

Answer:

a. B = 0.20T

b. u = 17230.6 J/m³

c. E = 0.236J

d. L = 5.84*10^-5 H

Explanation:

a. In order to calculate the magnetic field in the solenoid you use the following formula:

$B=\frac{\mu_o n i}{L}$ (1)

μo: magnetic permeability of vacuum = 4π*10^-7 T/A

n: turns of the solenoid = 460

L: length of the solenoid = 25.0cm = 0.25m

i: current = 90.0A

You replace the values of the parameters in the equation (1):

$B=\frac{(4\pi*10^{-7}T/A)(460)(90.0A)}{0.25m}=0.20T$

The magnetic field in the solenoid is 0.20T

b. The magnetic permeability of air is approximately equal to the magnetic permeability of vacuum. To calculate the energy density in the solenoid you use:

$u=\frac{B^2}{2\mu_o}=\frac{(0.20T)^2}{2(4\pi*10^{-7}T/A)}=17230.6\frac{J}{m^3}$

The energy density is 17230.6 J/m³

c. The total energy contained in the solenoid is:

$E=uV$ (2)

V is the volume of the solenoid and is calculated by assuming the solenoid as a perfect cylinder:

$V=AL$

A: cross-sectional area of the solenoid = 0.550 cm^2 = 5.5*10^-5m^2

$V=(5.5*10^{-5}m^2)(0.25m)=1.375*10^{-5}m^3$

Then, the energy contained in the solenoid is:

$E=(17230.6J/m^3)(1.375*10^{-5}m^3)=0.236J$

The energy contained is 0.236J

d. The inductance of the solenoid is calculated as follow:

$L=\frac{\mu_o N^2 A}{L}=\frac{(4\pi*10^{-7}T/A)(460)^2(5.5*10^{-5}m^2)}{0.25m}\\\\L=5.84*10^{-5}H$

The inductance of the solenoid is 5.84*10^-5 H

3 0

3 years ago

What are three ways to speed up a<br> reaction?

Ksju [112]

Explanation:

Increase the temperature in Endothermic reactions (Reactions that absorb energy, or become cold) Decrease the temperature in Exothermic reactions (Reactions that release energy, or become hot) Add a catalyst (A substance that reduces activation energy, speeding up the reaction) Increase the concentration of reactants.

source: https://socratic.org/questions/how-can-a-chemical-change-be-speeded-up

6 0

2 years ago

Read 2 more answers