1 ) Sand dunes on a desert island move as sand is swept up the windward side to settle in the leeward side. Such “walking” dunes have been known to travel 20 feet in a year and can travel as much as 100 feet per year in particularly windy times. Calculate the average speed in each case in m/s.

(b) Fingernails grow at the rate of drifting continents, about 10 mm/yr. Approximately how long did it take for North America to separate from Europe, a distance of about 3 000 mi?

a )

20ft = 32180m

average speed = 32180/100 = 321.8

b)

t = 3000/10 = 300

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2 ) A bristlecone pine tree has been know to take 4000 years to grow to a height of 20 ft.

a)Find the avearge speed of growth in m/s

b) In contrast the faster growing palnt is the gaint kelp which can grow at rate of 2 feet in one day

a )

4000 years conver to secound

=345.6X10^-6

now 20 ft to m = 6.1

avearge speed = 6.1/345.6X10^-6 = 1.7650

b) I don't understand this ?

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3 ) Two cars travel in the same direction along a straight highway, one at a constant speed of 55 mi/h and the other at 70 mi/h. (a) Assuming that they start at the same point, how much sooner does the faster car arrive at a destination 10 mi away? (b) How far must the faster car travel before it has a 15-min lead on the slower car?

give me the idea in this queation .