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November 10th, 2016, 01:46 PM   #1
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Kinetic Energy

I'm having trouble with calculating Kinetic Energy.

River water with a mass of 100 tonnes is moving at 12.5km/h. What is its kinetic energy?

E = 1/2mkw

I got 100000 x 3.47 X .5 = 1735000 j

But the real answer is suppose to be 602.7 kj.

I don't get it.
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November 10th, 2016, 02:11 PM   #2
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Quote:
Originally Posted by jayinwww View Post
I'm having trouble with calculating Kinetic Energy.

River water with a mass of 100 tonnes is moving at 12.5km/h. What is its kinetic energy?

E = 1/2mkw

I got 100000 x 3.47 X .5 = 1735000 j

But the real answer is suppose to be 602.7 kj.

I don't get it.
$E = \dfrac 1 2 m v^2~kg\cdot m/s^2$

$12.5 km/hr = 3.472 m/s$

$100 tonne = 100000 kg$

$E = \dfrac 1 2 (100000)(3.472)^2 = 602816.36 J = 602.8 kJ$
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Last edited by romsek; November 10th, 2016 at 02:15 PM.
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November 15th, 2016, 04:39 AM   #3
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Quote:
Originally Posted by jayinwww View Post
I'm having trouble with calculating Kinetic Energy.

River water with a mass of 100 tonnes is moving at 12.5km/h. What is its kinetic energy?

E = 1/2mkw
What do "m", "k", and "w" stand for?

Quote:
I got 100000 x 3.47 X .5 = 1735000 j

But the real answer is suppose to be 602.7 kj.

I don't get it.
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