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A piece of rope is placed on the ground at the equator and runs all the way round the Earth.It is then cut, and 1 metre is added.Now we ask everyone around Earth to stand equally placed apart and lift the rope,how high will they be able to lift it?

 May 11, 2015

Best Answer 

 #1
avatar+110 
+6

d = 12 472km

r = 6 236km

p = d * pi = 12472×π=39181.9435755719012701

 

Let's add a meter:

(1m = 1/1000km)

 

39181.94358+11000=39181.94458

 

And back to the diameter:

 

39181.94458π=12472.0003197193937865

 

We have ~3.197 Meter more.

We can lift it now by 1.5985 Meter on each side. 

 May 11, 2015
 #1
avatar+110 
+6
Best Answer

d = 12 472km

r = 6 236km

p = d * pi = 12472×π=39181.9435755719012701

 

Let's add a meter:

(1m = 1/1000km)

 

39181.94358+11000=39181.94458

 

And back to the diameter:

 

39181.94458π=12472.0003197193937865

 

We have ~3.197 Meter more.

We can lift it now by 1.5985 Meter on each side. 

xerxes May 11, 2015
 #2
avatar+33654 
+3

If h is the height it can be lifted, then we have:

 

Original circumference = pi*d  where d is diameter of the earth.

New circumference = pi*(d+2h)  since the new diameter is d+2h.

 

New - Old circumference:  pi*(d + 2h) - pi*d = 1m so that pi*2h = 1m  or h = 1/(2pi) m or h ≈ 0.159m

 

(xerxes, your next to last line should say "We have ∼0.3197 meters more).

.

 May 11, 2015
 #3
avatar+122 
+3

sorry xerxes,answer is simply     1metre/2pi.

Here's the solution; let Earth's circumference be 2pi R. New circumference then is 2pi (R + delta R) where delta R is the height we want to find.

so 2pi R + 1 metre= 2pi(R+ deltaR),the 2pi R 's cancel out,giving 2pi delta R = 1 metre,so delta R,the height,is 1 metre /2pi. We did not need to know the Earth's circumference in order to solve the problem.

 May 11, 2015

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