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 Energy and Work Energy and Work Physics Help Forum Aug 26th 2015, 12:10 PM #11 Junior Member   Join Date: Aug 2015 Posts: 3 If you guys don't mind, I had one more question that I'm probably overthinking as well. The answer to this question is D and I plugged in my own numbers to get that answer. However, I don't understand the concept. Why is it that dividing the velocity by two means you have to divide the Kinetic Energy by 4? I bolded "divide" because that's what "decrease by a factor" means to do. The kinetic energy E of an object is given by E = .5*m*v^2 where m is the object's mass and v is the velocity of the object. If the velocity of an object decreases by a factor of 2 what will happen its kinetic energy? A. Kinetic energy will increase by a factor of 2. B. Kinetic energy will increase by a factor of 4. C. Kinetic energy will decrease by a factor of 2. D. Kinetic energy will decrease by a factor of 4.   Aug 26th 2015, 12:55 PM #12 Physics Team   Join Date: Jun 2010 Location: Morristown, NJ USA Posts: 2,336 same principle as the earlier problem - the kinetic energy of an object is proportional to the velocity of the object squared. An object moving at 10 m/s has four times the KE of an object moving at half that speed. One way to see this is to calculate the ratio of the two energies: KE_1/K_2 = (0.5 m v_1^2)/(0.5 m v_2^2) = (v_1/v_2)^2 So if v_2 = one half v_1, then KE_2 = one quarter KE_1  Tags elastic, erroneous, problem, spring Thread Tools Show Printable Version Email this Page Display Modes Linear Mode Switch to Hybrid Mode Switch to Threaded Mode Similar Physics Forum Discussions Thread Thread Starter Forum Replies Last Post stalebhacine Advanced Thermodynamics 0 Mar 14th 2015 10:49 AM teddybear9 Energy and Work 1 Feb 1st 2012 07:24 AM teddybear9 Kinematics and Dynamics 2 Nov 15th 2011 12:09 PM nicefatsow Equilibrium and Elasticity 1 Oct 23rd 2009 09:06 PM rjsci13 Kinematics and Dynamics 1 Oct 13th 2009 02:50 AM