California has become the first U.S. state to approve plans to require newly-built homes to include solar equipment.

    The state's Energy Commission voted 5-0 to approve the new rules, which are to take effect in 2020. The rules will deal with most newly-built residential (住宅的) buildings up to three stories high.

    The move is California's latest step aimed at reaching renewable energy targets and reducing greenhouse gas emissions.

    California has set a goal of filling half of its electricity needs with renewable energy by 2030. Officials said they had reached 30 percent by the end of 2017. The state's Governor, Jerry Brown, plans to hold an international climate meeting in September.

    ①The Energy Commission said the cost of adding solar equipment to a single-family home would be about $9,500. But, the group added that homeowners would save at least $19,000 in energy costs over 30 years.

    Robert Raymer is the technical director for the California Building Industry Association. He says the action is a step forward for the wider use of solar power in the U.S. "You can bet every other of the 49 states will be watching closely to see what happens," he told the Associated Press.

    ②Solar companies praised the new requirements, which officials have said will likely raise demand for solar equipment in California by 10-15 percent.

    The Solar Energy Industries Association called it a "historic decision for the state and the U.S." It estimated the action would produce "huge economic and environmental benefits," including bringing tens of billions of dollars into California.

    ③Some legislative and community leaders argued that Californians cannot afford to pay any more for housing in what is already an extremely high-priced market.

    "That's just going to drive the cost up and make California, once again, not affordable to live in," said California Assemblyman Brian Dahle.

    ④Severin Borenstein is an energy economist at the University of California, in Berkeley. He sent an email to the head of California's Energy Commission to urge the state to reconsider its decision.

    He expressed his belief that it is a mistake for California to approve such a policy instead of centering on efforts to develop large solar farms to produce renewable energy. He said these farms would cost much less to operate.

    "Every energy economist I know is shaking their head at this," he told the Wall Street Journal. "In many ways, this is setting the wrong example," he added.

函数$y=\sqrt{9-{\left(x-5\right)}^2}$的图象上存在不同的三点到原点的距离构成等比数列，则以下不可能成为该等比数列的公比的数是（   ）

如图所示，细线的一端固定于O点，另一端系一小球，在水平拉力作用下，小球以恒定速率在竖直平面内由点B运动到点A．下列说法正确的是（   ）

物体的质量真的会不变吗?

在现有的物理知识的基础上,同学们会肯定地认为物体的质量是不会随形状、位置、状态的改变而改变的,物体的质量是常数.这个认识并没有错,但这是对静止的物体的质量而言. 如果对运动的物体而言,物体的质量是否还是始终不变呢?根据爱因斯坦的"相对论",运动的物体的质量会随它的运动速度而改变.他的理论是:设一个物体静止时的质量为m₀(又称为静质量),当它以速度v运动时的质量为m(又称为动质量),则动质量与静质量及其速度的关系遵循以下规律：

$m=\frac{m_0}{\sqrt{1-{\left(\frac{v}{c}\right)}^2}}\left(其中c为光速\right)$

根据以上公式我们可以计算出：

一个静质量m₀=1kg的物体，当它以v₁=300m/s和v₂=15×10⁴km/s 运动时,其动质量分别为: m₁=1.000 000 000 0005kg、m₂=1.15kg，由此可知,物体的动质量比静质量大,且物体的运动速度越大,其动质量越大.从m₁值可看出,在低速(相对光速而言)范围内,物体的动质量与静质量相关甚微,其差值可以忽略不计.因此在低速范围内研究宏观物体的运动情况时,可以认为物体的质量是不变的,是常数.

但在微观世界里,由于电子、质子等基本粒子的静质量都很小,而其运动速度又很容易接近光速,这时它们的质量随速度的改变就不可忽视.关于这样的问题,同学们将来有机会学习爱因斯坦的"相对论"力学知识时,就会进一步深入理解.

请根据刚才的阅读,回答下列问题：