12.6 In 2014, Ben Winger at the University of Michigan and his colleagues built a mathematical model to _________  the geographical ranges of the ancestors of hundreds of living species of American songbird.

12.4 Some common swifts flying across the Mediterranean and the Sahara Desert took more than two months to complete the southern journey in autumn, while __________.

12.3 One theory is that it comes down to _______.

12.2 But that raises another question: why do these birds risk their lives ________ ?

Choose a word or sentence for each gap that best fits the text context.

THE Arctic tern, a black-crowned seabird weighing no more than a bar of soap, flies from the top of the world to the bottom and back again every year. That’s 40,000 kilometres as the crow flies. But when researchers equipped terns with satellite tracking devices, they discovered that  1. . One individual ended up covering close to 100,000 kilometres – equivalent to more than twice around the planet.

Why bother to migrate?

One theory is that it comes down to 3.. “In the tropics, competition for nesting space is fierce,” says Anders Hedenström at Lund University in Sweden. “So it may well pay to opt out of that fight and fly north, where the food supply peaks in summer and there is more room for nesting – at least if you get there in time, because the best spots may get filled fairly rapidly.”

That might explain why many migratory birds are in such a hurry during their spring migration. Some common swifts flying across the Mediterranean and the Sahara Desert took more than two months to complete the southern journey in autumn, while 4..

Then again, in terms of the 5. of intercontinental migration, it’s far from clear that all birds making these journeys today started out travelling north from the tropics during the summer. In 2014, Ben Winger at the University of Michigan and his colleagues built a mathematical model to 6. the geographical ranges of the ancestors of hundreds of living species of American songbird. They found that most long-distance migrants began in the north and started flying south for winter, as opposed to being tropical birds flying north for summer.

All of which still leaves open the question of why some species 7.. Why not find somewhere closer for a winter escape? We’re still a world away from a conclusive answer. One idea is that favourable winter-summer habitats 8. as a result of the movement of continents, forcing birds to cover just a few extra millimetres each year – but vast distances millions of years later.

12.1 But when researchers equipped terns with satellite tracking devices, they discovered that _________.

The world record for the 100m sprint, held by Usain Bolt, is 9.58 seconds.

With this information alone, i.e. without using extra information about the accuracy of Olympic sprint track timing and distances, which of the following is the correct statement about his average speed and its uncertainty?

Hint I: The average speed can be calculated from v = d/t.

Hint II: For given data where no other uncertainty information is provided, a reasonable estimate of the uncertainty will generally be:

            ½ (last significant figure)

This means that you should take the distance to be d = 100.0 ± 0.5 m and the time to be t = 9.580 ± 0.005 s.

Hint III: Refer to the section on combining uncertainties in the Guide to Experimental Work.

The following data is recorded for the oscillation period of a pendulum

The average value is 5.29 s, what is the absolute uncertainty in seconds? For the purpose of this quiz, do not include the unit in your answer, just the numerical value.

Hint: you might find it useful to open an Excel spreadsheet to answer this.

Ознаки потенціальної сили.

.... you going to be at the club this evening?