Questions

Rolling friction or rolling drag is the force resisting the motion when a body rolls on a surface. It is mainly caused by non-elastic effects, that is, not all the energy needed for deformation of the wheel, roadbed, etc... is recovered when the pressure is removed.

Another cause of rolling resistance lies in the slippage between the wheel and the surface, which dissipates energy.

Peggy Whitson on 24 April 2017 broke the record for most days spent in space (cumulatively) by a US astronaut. She broke the previous record set by Jeff Williams who had spent a total of 534 days in space.

– Whitson has been currently living and working aboard the International Space Station (ISS), for which she was launched in November 2016 using a Russian Soyuz capsule. At the time of her launch, she had already accumulated 377 total days in space.

– Her mission was recently extended for an additional three months. Now when she will return from ISS in September 2017, she would have accumulated more than 600 days in space.

It is MISSISSIPPI.

In a first, China is planning to send mini-ecosystems — containing potato seeds and silkworm eggs — to the Moon next year, in an attempt to study how the organisms develop on the lunar surface. The 3-kilogramme mini-ecosystem, developed by research teams led by Chongqing University in China, will be sent to the Moon by the Chang’e 4 scheduled to be launched in 2018, authorities announced at the Global Space Exploration Conference. An 18-centimetre-tall cylinder will carry potato seeds and silkworm eggs to be incubated.

Heritable variation is one of the four most important factors that affect whether natural selection can occur. These factors include

1) Heritable variation

2) Descent with modification

3) Struggle for survival, and necessarily if the others are satisfied

4) Survival of the fittest.

Heritable variation allows for possibly beneficial, negative, or even neutral mutations to get filtered during each generation by natural selection--weeding out negative mutations, passing on positive and neutral ones. Without heritable variation, species would quickly fall victim to parasites who take advantage of identical genetic material in a population and evolution would not occur.

Variation is the raw material of evolution.