(FUVEST 2009 1ª FASE) Ao longo da evolução das plantas, os gametas

Em 1839, o físico Alexandre Edmond Becquerel (1820–1891) ao descobrir, experimentalmente, o efeito fotoelétrico, aos 19 anos de idade, jamais imaginou que estivesse criando um novo meio de captação de energia limpa. A energia solar incide sobre uma célula fotoelétrica atingindo elétrons e produzindo eletricidade que pode ser convertida em energia luminosa ou mecânica, por exemplo. Para garantir maior eficiência, o material usado na fabricação de uma célula fotoelétrica deve ter

(CEFET MG) 

Constantes físicas

Aceleração da gravidade: g = 10 m/s²

Velocidade da luz no vácuo: c = 3,00 x 10⁸ m/s

Constante da lei de Coulomb: k₀ = 9,0 x 10⁹ N.m² / C²

Um foguete é lançado de um planeta de massa M e raio R. A velocidade mínima necessária para que ele escape da atração gravitacional e vá para o espaço é dada por

O Movimento dos Trabalhadores Rurais sem Terra (MST) foi criado em 1984, inserido em um contexto de:

(UNESP) Question: Is there anything I can do to train my body to need less sleep?

Karen Weintraub

June 17, 2016

Many people think they can teach themselves to need less sleep, but they’re wrong, said Dr. Sigrid Veasey, a professor at the Center for Sleep and Circadian Neurobiology at the University of Pennsylvania’s Perelman School of Medicine. We might feel that we’re getting by fine on less sleep, but we’re deluding ourselves, Dr. Veasey said, largely because lack of sleep skews our self-awareness. “The more you deprive yourself of sleep over long periods of time, the less accurate you are of judging your own sleep perception,” she said.

Multiple studies have shown that people don’t functionally adapt to less sleep than their bodies need. There is a range of normal sleep times, with most healthy adults naturally needing seven to nine hours of sleep per night, according to the National Sleep Foundation. Those over 65 need about seven to eight hours, on average, while teenagers need eight to 10 hours, and school-age children nine to 11 hours. People’s performance continues to be poor while they are sleep deprived, Dr. Veasey said.

Health issues like pain, sleep apnea or autoimmune disease can increase people’s need for sleep, said Andrea Meredith, a neuroscientist at the University of Maryland School of Medicine. A misalignment of the clock that governs our sleep-wake cycle can also drive up the need for sleep, Dr. Meredith said. The brain’s clock can get misaligned by being stimulated at the wrong time of day, she said, such as from caffeine in the afternoon or evening, digital screen use too close to bedtime, or even exercise at a time of day when the body wants to be winding down.

(http://well.blogs.nytimes.com. Adaptado.) 

No trecho do primeiro parágrafo “We might feel that we’re getting by fine on less sleep”, o termo em destaque pode ser substituído, sem alteração de sentido, por: