PHYSICS HIGH SCHOOL

In which of the following sentences is work used in the scientific sense of the word? A scientist works on an experiment in the laboratory.*

B Sam and Rachel pushed, but they could do no work on the car. ????

Answers

Answer 1
Answer: B) obviously. Work in a scientific sense is the ability to make a displacement on an object in this case.

In A) the scientist can work on an experiment as your uncle can work on the field planting tomatos.

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Scientific notation 47,000

what is the kinetic energy of an object that has mass of 30 kilograms and move with a velocity of 20 m/s

Answers

Kinetic Energy = 1/2 * m * v² 1/2 * 30 * 20² 1/2 * 30 * 400 12000/2 6000 J.

A student who weighs 550 N is wearing a backpack that weighs 80 N. The student is standing still on level ground. Give your answers to the following questions in newtons. Remember, enter only the number; don't try to enter the units.a) What is the magnitude of the net force on the student?b) What is the magnitude of the contact force on the student by the backpack?
c) What is the magnitude of the contact force on the student by the ground?

Answers

Answer:

Explanation:

a) The magnitude of the net force on the student = 0 N since the student is standing still on level ground and upward reaction force = downward force.

b) the magnitude of the contact force on the student by the backpack = 80 N since the student was backing the backpack

c) the magnitude of the contact force o the student by the ground = 550 N + 80 N = 630 N reactional force on the student

Which of these discoveries is generally attributed to newtonA).The force of gravity acts between any two objects
B). The earth is round
C). Planets Move In circles
D). The orbit of mars is an ellipse

Answers


Most people know that Newton said "A).".

Most people DON't know that Newton showed that
IF "A)." is true, then "D)." must also be true.  Of all the planets.
A. is the answer to the question 

A container holding 1.2 kg of water at 20.0 °C is placed in a freezer that is kept at –20.0 °C. The water freezes and comes into thermal equilibrium with the interior of the freezer. a) How much heat is extracted from the water in thisprocess?
b) What is the minimum amount of electrical energy required bythe refrigerator to carry out this process if it operates betweenreservoirs at temperatures of 20.0 °C and -20.0 °C?

Answers

Answer:

(a) Q=556464\ J

(b) 556464 joule

Explanation:

Given:

  • mass of water, m_w=1.2\ kg
  • initial temperature of water, T_i=20^(\circ)C
  • final temperature of frozen water, T_f=-20{}^(\circ)C

The conversion of water of 20.0 °C to the ice of –20.0 °C will comprise of three steps:

  1. cooling of water to 0 °C Q_w
  2. formation of ice at 0 °C from the water of 0 °C Q_L
  3. further cooling of ice of 0 °C to -20 °C Q_i

We have,

  • Latent heat of fusion of ice, L=3.4* 10^5\ J.kg^(-1)
  • specific heat of water, c_w=4186\ J.kg^(-1).^(\circ)C^(-1)
  • specific heat of ice, c_i=2000\ J.kg^(-1).^(\circ)C^(-1)

(a)

Now, total heat lost in the process:

Q=Q_w+Q_L+Q_i

Q=m_w(c_w. \Delta T_w+L+c_i.\Delta T_i)

where:

\Delta T_i\ \&\ \Delta T_w = change in temperature of ice and water respectively.

\Rightarrow Q=1.2(4186* 20+3.4* 10^5+2000* 20)

Q=556464\ J is the total heat extracted during the process.

(b)

So, 556464 joule is the minimum electrical energy (by the law of energy conservation under no loss condition) required by refrigerator to carry out this process if it operates between the reservoirs at temperatures of 20.0 °C and -20.0 °C, because for a refrigerator to work in a continuous cycle it is impossible to transfer heat from a low temperature reservoir to a high temperature reservoir without consuming energy in the form of work. Here 556464 joule is the heat of the system to be eliminated.

Final answer:

The amount of heat extracted from the water involves the sum of heat lost as it cools and then freezes. The minimum energy needed by the refrigerator to do this is given by the formula for Carnot efficiency.

Explanation:

To answer these questions, we'll need to understand some fundamental principles of thermodynamics.

a) The heat Q taken from the water will be the sum of the heat released during cooling of the water until 0.0°C, and the heat released during freezing at 0.0°C. The heat loss as the water cools can be calculated using Q = mcΔt where m=mass of water, c=specific heat of water, and Δt=change in temperature. The heat loss as water freezes can be calculated using Q = mlf where lf is the latent heat of fusion. Adding these two quantities gives the total heat extracted.

b) The minimum energy needed by the refrigerator, W, is given by the Carnot efficiency formula, W = Q*(T_hot - T_cold)/T_hot, where T is in Kelvin. This would tell you how much energy the refrigerator needs to remove the heat from the water and cool it down to the freezer temperature.

Learn more about Thermodynamics here:

brainly.com/question/35546325

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What is the measurement 111.009 mm rounded off to four significant digits?

Answers

111.0 because 111.009 rounds off to 111.01, thus rounding again off to 111.0

Answer:

It is b. 111.0 mm

Explanation:

ok

A mass of gas has a volume of 4m3, a temperature of 290k, and an absolute pressure of 475 kpa. When the gas is allowed to expand to 6.5m3, it's new temperature is 277K. What's the absolute pressure of the gas after expansion?

Answers

Given:

V1 = 4m3

T1 = 290k

P1 = 475 kpa = 475000 Pa

V2 = 6.5m3

T2 = 277K

Required:

P

Solution:

n = PV/RT

n = (475000 Pa)(4m3) / (8.314 Pa-m3/mol-K)(290k)

n = 788 moles

P = nRT/V

P  = (788 moles)(8.314 Pa-m3/mol-K)(277K)/(6.5m3)

P = 279,204 Pa or 279 kPa
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