PHYSICS COLLEGE

Before the development of quantum theory, Ernest Rutherford's experiments with gold atoms led him to propose the so-called Rutherford Model of atomic structure. The basic idea is that the nucleus of the atom is a very dense concentration of positive charge, and that negatively charged electrons orbit the nucleus in much the same manner as planets orbit a star. His experiments appeared to show that the average radius of an electron orbit around the gold nucleus must be about 10−1010−10 m. Stable gold has 79 protons and 118 neutrons in its nucleus. What is the strength of the nucleus' electric field at the orbital radius of the electrons?
What is the kinetic energy of an electron in a circular orbit around the gold nucleus?

Answers

Answer 1

Answer:

Answer:

a) F = -1.82 10⁻¹⁵ N, b) K = 9.1 10⁻¹⁶ J

Explanation:

a) To calculate the force between the nucleus and the electrons, let's use the Coulomb equation

F = k q Q / r²

as the nucleus occupies a very small volume compared to electrons, we can suppose it as punctual

let's calculate

F = 9 10⁹ (-1.6 10⁻¹⁹) (79 1.6 10⁻¹⁹) / (10⁻¹⁰)²

F = -1.82 10⁻¹⁵ N

b) they ask us for kinetic energy

let's use Newton's second law

F = m a

acceleration is centripetal

a = v² / r

we substitute

F = m v² / r

v = √ (F r / m)

v = √ (1.82 10⁻¹⁵ 10⁻¹⁰ / 9.1 10⁻³¹)

v = √ (0.2 10⁻¹⁶)

v = 0.447 10⁸ m / s

kinetic energy is

K = ½ m v²

K = ½ 9.1 10⁻³¹ (0.447 10⁸)²

K = 0.91 10⁻¹⁵ J

K = 9.1 10⁻¹⁶ J

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The heating element of a coffeemaker operates at 120 V and carries a current of 4.50 A. Assuming the water absorbs all of the energy converted by the resistor, calculate how long it takes to heat 0.525 kg of water from room temperature (23.0°C) to the boiling point.

A 30 W engine generates 3600 J of energy. How long did it run for?

Answers

Answer:

so the time taken will be 120 seconds

Explanation:

power=30W

work done=3600J

time=?

as we know that

$power=(work done)/(time taken)$

evaluating the formula

power×time taken=work done

$time taken=(work done)/(power)$

$time taken=(3600J)/(30W)$

$Time taken=120seconds$

i hope this will help you :)

You know that you sound better when you sing in the shower. This has to do with the amplification of frequencies that correspond to the standing-wave resonances of the shower enclosure. A shower enclosure is created by adding glass doors and tile walls to a standard bathtub, so the enclosure has the dimensions of a standard tub, 0.75 m wide and 1.5 m long. Standing sound waves can be set up along either axis of the enclosure. What are the lowest two frequencies that correspond to resonances on each axis of the shower? These frequencies will be especially amplified. Assume a sound speed of 343 m/s.

Answers

Answer: Length axis f= 114.3 Hz, Width axis f=228.67 Hz

Explanation:

We are given that,

Length of tub= 1.5 m

Width of tub= 0.75 m

Sound speed= 343 m/s

Now, we are also given shower is closed.

So, frequency is given as:

f= $m* (v)/(2L)$

For length axis

Put v= 343 m/s, m=1 and L=1.5 m

f= 1 * $(343)/(2*1.5)$

f= 114.3 Hz

For next resonant frequency, m=2

f= 2* $(343)/(2*1.5)$

f= 228.67

For width axis

Put v= 343 m/s, m=1 and L= 0.75 m

f= 1* $(343)/(2*0.75)$

f= 228.67 Hz

For next frequency, m=2

f= 2* $(343)/(2*0.75)$

f= 457.34 Hz

A force of 200N acts on a body that moves along a horizontal plane in the same direction of movement. The body moves 30m. What is the work done by that force?

Answers

Work = Force times Distance

Work = 200 x 30

Work = 6000

The work done by a force of 200N on a body that moved 30m is 6000J or 6000 Joules.

PLEASE HELP QUICKLY!A volleyball player jumps to hit a ball horizontally at 7.0 m/s straight on. If the
height at which the ball was hit is 3.0 m tall, how far did the ball go horizontally
before it hit the ground?
5.5 m
3.6 m
O 4.3 m
4.2 m

Answers

Answer:

5.5 is the correct answer

please keeps as Brainly list

We start with 5.00 moles of an ideal monatomic gas with an initial temperature of 129 ∘C. The gas expands and, in the process, absorbs an amount of heat equal to 1180 J and does an amount of work equal to 2160 J . What is the final temperature Tfinal of the gas? Use R = 8.3145 J/(mol⋅K) for the ideal gas constant.

Answers

The final temperature of an ideal monatomic gas with an initial temperature of 128°C. is 114.53°C.

From the first law of thermodynamics,

ΔU=Q - W

Where,

ΔU - change in internal energy

Q - energy absorbed

W - work

So,

ΔU = 1180 J - 2020 J

ΔU = -840 J

From ideal gas law

$\bold {\Delta U = \frac 32n R (T_2- T_1)}}\n\n\bold {T_ 2 = \frac {2\Delta U}{3nR} +T_1}$

Where, T2 is the final temperature,

n- moles of gas

R - gas constant

T1 - initial temperature,

Put the values in the equation

$\bold {T_ 2 = \frac {2* -840\ J )}{3* 5 * 8.314\ J/mol.K} + 128^oC}\n\n\bold {T_2 = 114.53 ^oC}$

Therefore, the final temperature of an ideal monatomic gas with an initial temperature of 128°C. is 114.53°C.

To know more about ideal gas law,

brainly.com/question/6534096

The solution is in the attachment

An indestructible bullet 2.00cm long is fired straight through a board that is 10.0cm thick. The bullet strikes the board with a speed of 470 m/s and emerges with a speed of 270 m/s. (To simplify, assume that the bullet accelerates only while the front tip is in contact with the wood.) a). What is the average acceleration of the bullet through the board? ________m/s^2b). What is the total time that the bullet is in contact with the board? (Enter the total time for the bullet to completely emerge from the board.) _________s
c.) What thickness of board (calculated 0.1 cm) would it take to stop the bullet, assuming that the acceleration through all boards is the same? ________cm