College Physics Problem 1.9

Tectonic plates are large segments of the Earth’s crust that move slowly. Suppose that one such plate has an average speed of 4.0 cm/year.
(a) What distance does it move in 1.0 s at this speed?
(b) What is its speed in kilometers per million years?

SOLUTIONS:

a) We know that the formula for the distance traveled, d, if we are given rate, r, and time, t is given by d=rtimes t.

Therefore, the distance traveled is 

d= frac{4.0cm}{year}times 1 sectimes frac{1 m}{100 cm} times frac{1 year}{362.25 days} times frac{1 day}{3600 s}=1.3times10 ^{-9} m

Therefore, the distance traveled by the tectonic plate is about 1.3times10^{-9} meters.

b) We need to convert 4.0 cm/year to km/My. 

frac{4.0cm}{year}times frac{1m}{100 cm } times frac{1km}{1000 m} times frac{10^{6}year}{1My}=40 km/My

Therefore, the speed of the tectonic plates is 40 km/My.

 

 

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