Một vật dao động điều hòa có phương trình là x = 4sin(πt + π/3) (cm; s). Lúc t = 0,5s vật có li độ và vận tốc là

Uest<br>1. State Newton's law of cooling.

garik1379 [7]

Answer:

Newton's law of cooling states that the rate of heat loss of a body is directly proportional to the difference in the temperatures between the body and its surroundings. The law is frequently qualified to include the condition that the temperature difference is small and the nature of heat transfer mechanism remains the same. As such, it is equivalent to a statement that the heat transfer coefficient, which mediates between heat losses and temperature differences, is a constant. This condition is generally met in heat conduction (where it is guaranteed by Fourier's law) as the thermal conductivity of most materials is only weakly dependent on temperature. In convective heat transfer, Newton's Law is followed for forced air or pumped fluid cooling, where the properties of the fluid do not vary strongly with temperature, but it is only approximately true for buoyancy-driven convection, where the velocity of the flow increases with temperature difference. Finally, in the case of heat transfer by thermal radiation, Newton's law of cooling holds only for very small temperature differences.

When stated in terms of temperature differences, Newton's law (with several further simplifying assumptions, such as a low Biot number and a temperature-independent heat capacity) results in a simple differential equation expressing temperature-difference as a function of time. The solution to that equation describes an exponential decrease of temperature-difference over time. This characteristic decay of the temperature-difference is also associated with Newton's law of cooling

6 0

3 years ago

If i have a kinematic equation vf^2=vi^2-2*a(xf-xi), how can i solve for xi step by step

azamat

Answer:

Explanation:

$v_f^2 = v_i^2-2a(x_f-x_i)$

Subtract both sides by $v_i^2$ :

$- v_i^2+v_f^2 = -2a(x_f-x_i)$

Divide both sides by -2*a:

$\frac{v_i^2 - v_f^2}{2a} =x_f-x_i$

Add both sides by $x_i$ :

$x_i+\frac{v_i^2 - v_f^2}{2a} =x_f$

Subtract both sides by $\frac{v_i^2 - v_f^2}{2a}$ :

$x_i=x_f-\frac{v_i^2 - v_f^2}{2a}$

8 0

3 years ago

Sics and Chemistry A (2nd Six Weeks) - SC3200SFA/01

Andreyy89

Force = Mass * Acceleration therefore the red ball with the higher mass will have more force and greater acceleration

3 0

3 years ago

plz tell fast oktwo paragraphs describing the advantages and disadvantages of living in the town.plz tell

mars1129 [50]

Answer:

There are advantages and disadvantages to living in a small town. You are likely to have more frequent contact with neighbors in a small town than you would in a larger town or city, so it is important to take into account the pros and cons of having privacy. Also take into consideration other factors, including your plans for a family, the career opportunities, your finances, the schools and entertainment options. Your personality will determine whether a small town offers advantages or disadvantages.

Privacy

Many people who reside in small towns enjoy the closeness of knowing their neighbors and the details of neighbors' lives. If a baby is born, a child is ill or a relative dies, people in small towns often want to know about it and be there for you. This can be an advantage, especially if you are lacking a family of your own or enjoy a great deal of socializing. However, if you would rather keep the details of your life to yourself and turn your nose up at idle gossip, small town living might not be for you.

Finances

Jobs can be hard to come by in small towns. You might be required to commute out of town to work but then return to a peaceful environment at the end of a busy day. Housing might be cheaper in small towns, although commuting costs might be higher. Food and child care expenses might be reduced as people are more likely to have gardens and share produce or take turns watching each other's children.

Recreation

One of the disadvantages of a small town is not being close to amusement parks, zoos or museums. However, people in small towns tend to come together during town picnics, festivals or fairs. Depending on your preferences, small towns might provide a relaxed, slower pace when it comes to entertainment compared to the hustle and bustle of a city, where there is constant movement, commotion and entertainment at every corner.

Schools

In a small town, class sizes are usually smaller and teachers and students can get to know each other and their fellow classmates on a deeper level. Many small towns have schools that receive national academic awards or are the highest achieving district in their states. CNN Money ranked Louisville, Colorado as the number one small town in America in 2011 and the school system is academically ranked among the top three in the Denver area. However, some of these towns noted high taxes as a trade-off for the outstanding school systems.

Explanation:

3 0

3 years ago

A charged balloon will stick to a neutral wall. which process is involved?

Leokris [45]

<span>The charged balloon will stick to a neutral wall because of the Static Electricity:
</span>
The matter is formed by atoms and these atoms are composed of electrons, protons and neutrons (the electrons have a negative charge, the protons have a positive charge and the neutrons have no charge).

As the balloon is charged (It gained electrons), and the charge of the same sign repel each other, when it approaches the wall, the electrons of this wall will move away, and the positive charges (protons) will remain in the nearest area to the balloon. As the charges of different signs are attracted, the balloon will be stuck to the wall.

3 0

3 years ago