(UNIT) Sabe-se que, para o ouvido humano, a mínima intensidade sonora perceptível é de 10^-16 W/cm² e a máxima intensidade suportável, sem dor, é de 10^-4 W/cm². Uma pessoa afastada de uma fonte sonora que produz sons que se propagam uniformemente em todas as direções do espaço, começa a perceber o som de intensidade mínima quando se encontra a uma distância de 500,0 m.

Nessas condições, a menor distância da fonte a que a pessoa pode aproximar-se, sem sentir dor, é igual, em mm, a

Em muitos animais, machos e fêmeas da mesma espécie apresentam diferenças morfológicas ou comportamentais evidentes. Um exemplo clássico de dimorfismo sexual é o caso do pavão, em que o macho possui cauda vistosa e penas coloridas, as quais estão ausentes nas fêmeas. Em outras espécies, os machos possuem chifres, garras ou dentes maiores do que as fêmeas, e utilizam essas estruturas em combates físicos para defender territórios e ter acesso a fêmeas coespecíficas e receptivas.

Esse padrão de dimorfismo evolui porque

(ESPM) Emerging economies 

The Great Deceleration

The emerging-market slowdown is not the beginning of a bust. But it is a turning-point for the world economy

WHEN a champion sprinter falls short of his best speeds, it takes a while to determine whether he is temporarily on poor form or has permanently lost his edge. The same is true with emerging markets, the world economy’s 21st-century sprinters. After a decade of surging growth, in which they led a global boom and then helped pull the world economy forwards in the face of the financial crisis, the emerging giants have slowed sharply.

China will be lucky if it manages to hit its official target of 7.5% growth in 2013, a far cry from the double-digit rates that the country had come to expect in the 2000s. Growth in India (around 5%), Brazil and Russia (around 2.5%) is barely half what it was at the height of the boom. Collectively, emerging markets may (just) match last year’s pace of 5%. That sounds fast compared with the sluggish rich world, but it is the slowest emerging-economy expansion in a decade, barring 2009 when the rich world slumped.

This marks the end of the dramatic first phase of the emerging-market era, which saw such economies jump from 38% of world output to 50% (measured at purchasing-power parity, or PPP) over the past decade. Over the next ten years emerging economies will still rise, but more gradually. The immediate effect of this deceleration should be manageable. But the longer-term impact on the world economy will be profound.

 Running out of puff

 In the past, periods of emerging-market boom have tended to be followed by busts (which helps explain why so few poor countries have become rich ones). A determined pessimist can find reasons to fret today, pointing in particular to the risks of an even more drastic deceleration in China or of a sudden global monetary tightening. But this time a broad emerging-market bust looks unlikely.

China is in the midst of a precarious shift from investment-led growth to a more balanced, consumption-based model. Its investment surge has prompted plenty of bad debt. But the central government has the fiscal strength both to absorb losses and to stimulate the economy if necessary. That is a luxury few emerging economies have ever had. It makes disaster much less likely. And with rich-world economies still feeble, there is little chance that monetary conditions will suddenly tighten. Even if they did, most emerging economies have better defences than ever before, with flexible exchange rates, large stashes of foreign-exchange reserves and relatively less debt (much of it in domestic currency).

That’s the good news. The bad news is that the days of record-breaking speed are over. China’s turbocharged investment and export model has run out of puff. Because its population is ageing fast, the country will have fewer workers, and because it is more prosperous, it has less room for catch-up growth. Ten years ago China’s per person GDP measured at PPP was 8% of America’s; now it is 18%. China will keep on catching up, but at a slower clip.

That will hold back other emerging giants. Russia’s burst of speed was propelled by a surge in energy prices driven by Chinese growth. Brazil sprinted ahead with the help of a boom in commodities and domestic credit; its current combination of stubborn inflation and slow growth shows that its underlying economic speed limit is a lot lower than most people thought. The same is true of India, where near-double-digit annual rises in GDP led politicians, and many investors, to confuse the potential for rapid catch-up (a young, poor population) with its inevitability. India’s growth rate could be pushed up again, but not without radical reforms—and almost certainly not to the peak pace of the 2000s.

Jul 27th 2013/www.economist.com

The pronoun they in the underlined sentence of the fifth paragraph of the text: “Even if they did, …” refers to  

Um porta-lápis de madeira foi construído no formato cúbico, seguindo o modelo ilustrado a seguir. O cubo de dentro é vazio. A aresta do cubo maior mede 12 cm e a do cubo menor, que é interno, mede 8 cm.

Observe o perfil de uma montanha russa representado nesta figura

Um carrinho é solto do ponto M, passa pelos pontos N e P e só consegue chegar até o ponto Q. Suponha que a superfície dos trilhos apresenta as mesmas características em toda a sua extensão. Sejam E(cn) e E(cp) as energias cinéticas do carrinho, respectivamente, nos pontos N e P e E(tp) e E(tq) as energias mecânicas totais do carrinho, também respectivamente, nos pontos P e Q. Considerando-se essas informações, é CORRETO afirmar que: