PHYSICS HIGH SCHOOL

Johannes Kepler is best known for his work on planetary motion.
a. True
b. False

Answers

Answer 1
Answer:

Answer: True.

Kepler was an astronomer, astrologer and mathematician. He was an apprentice of Tycho Brahe, other big (maybe the biggest) astronomer of their time.

Kepler is best known for his 3 laws of planetary motion.

1) the orbit of a planet is an ellipse with the Sun at one of the two foci

2) A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time

3) The square of the orbital period of a planet is directly proportional to the cube of the semi-major axis of its orbit.
Answer 2
Answer: Truer words are seldom if ever written.

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Two charged objects, A and B, exert an electric force on each other. What happens if the distance between them is increased?

Answers

The correct answer to the question will be that the electric force between them will be decreased.

EXPLANATION:

Let us consider the charge contained by A and B are denoted as Q and Q' respectively.

Let R is the separation distance between them.

As per Coulomb's law in electrostatics, the force of attraction or repulsion between the two charge bodies A and B  will be -

           Coulombic force F = (1)/(4\pi \epsilon) (QQ')/(R^2)

Here, \epsilon is the permittivity of the medium in which the charges are present.

From above, we see that electric force is inversely proportional to the square of separation distance between them.

Mathematically it can be written:  F\ \alpha\ (1)/(R^2)

As per the question, the distance between A and B is increased.

Hence, the electric force between A and B will be decreased.
I agree with Hussein but I would like to add that when the distance between two charged objects increase, the force decreases by the Coulomb` s Law:
F= k * Q1*Q2 / r^2
where k is constant Q1, Q2-quantity of electricity and r- distance between two charged objects. So when you increase r, you divide with greater number and result decreases.
F=k(q1 * q2)/( r^(2) )

How would an electron shell model of an oxygen atom (O) appear after the atom has formed chemical bonds?

Answers

Since oxygen is found in group 6, it can be said that it will form 2 covalent bonds in order to complete its valency of 8 electrons. When it has formed chemical bonds, its electron shell model will show two atoms attached to oxygen, sharing 2 electrons. If oxygen bonds with only 1 atom (ex. CO), it will show 3 electrons being shared.

Answer:

A

Explanation:

If the abosolute of a gas is 600 k, the temperature in degrees Celsius is

Answers


Absolute Zero (Zero Kelvin) = -273.15° Celsius.

Zero° Celsius = 273.15 Kelvin .

600 K  =  (600 - 273.15°) = 326.85°C.

Two waves are superposed. One wave has an amplitude of 3 cm, and the other has an amplitude of 4 cm. What is the resultant amplitude?

Answers

The sum (or difference) of two solutions of the wave equation is again a solution of the wave equation(superposition principle)

therefore the amplitude of resultant wave is 3+4= 7cm

Answer:

7 cm

Explanation:

When the waves are super-posed their amplitudes are added algebraically to get the resultant amplitude.

resultant amplitude = 3+4 = 7cm

Streams of electrically charged particles flowing at high speeds from the sun make up the

Answers

That's the so-called 'solar wind'.

Four power transistors, each dissipating 12 W, are mounted on a thin vertical aluminum plate 22 cm 3 22 cm in size. The heat generated by the transistors is to be dissipated by both surfaces of the plate to the surrounding air at 25°C, which is blown over the plate by a fan. The entire plate can be assumed to be nearly isothermal, and the exposed surface area of the transistor can be taken to be equal to its base area. If the average convection heat transfer coefficient is 25 W/m2·K, determine the temperature of the aluminum plate. Disregard any radiation effects.

Answers

Answer:

The temperature of the Aluminium plate 44.84⁰C

Explanation:

Number of transistors = 4

Since the heat dissipated by each transistor is 12W

Total heat dissipated, Q = 4 * 12 = 48 W

Q = 48 W

Cross sectional Area of the Aluminium plate, A = 2(l * b)

l = Length of the aluminium plate = 22 cm = 0.22 m

b = width of the aluminium plate = 22 cm = 0.22 m

A =2( 0.22 * 0.22 )

A = 0.0968 m²

From the heat balance equation, Q = hAΔT

h = 25 W/m²·K

A = 0.0968 m²

ΔT = T - T(air)

T(air) = 25°C

ΔT = T - 25°C

Q = 25 * 0.0968 * (  T - 25)

Q = 2.42 (T - 25)

Substitute Q = 48 into the equation above

48 =  2.42 (T - 25)

T - 25 = 19.84

T = 25 + 19.84

T = 44.84 ⁰C
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