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 Periodic and Circular Motion Periodic and Circular Motion Physics Help Forum Jul 10th 2014, 10:26 PM #1 Junior Member   Join Date: Jun 2014 Posts: 19 Frequency calculation- need help! Hi there, I'm really struggling with the below question. The mass of a car is 1250kg and the mass of the driver is 80kg. When the driver sits on the seat, the suspension system of the car compresses by 0.02m. The car (with the drier sitting in it) is then pushed down by another person and let go, causing the car to oscillate up and down. Show that the frequency of the oscillation of the car is 0.864 Hz (3 s.f) Okay, so what I did was calculate K from F=ky, using m x g for force (I combined the mass so it was 1330kg). Then I used the T equation (using mass and K). Then I thought frequency could just be calculated from f= 1/T, but I get a completely different answer to what I need to show. Any help is really appreciated! Thanks so much.    Jul 11th 2014, 01:43 PM   #2
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 Originally Posted by Fizzle Hi there, I'm really struggling with the below question. The mass of a car is 1250kg and the mass of the driver is 80kg. When the driver sits on the seat, the suspension system of the car compresses by 0.02m. The car (with the drier sitting in it) is then pushed down by another person and let go, causing the car to oscillate up and down. Show that the frequency of the oscillation of the car is 0.864 Hz (3 s.f) Okay, so what I did was calculate K from F=ky, using m x g for force (I combined the mass so it was 1330kg). Then I used the T equation (using mass and K). Then I thought frequency could just be calculated from f= 1/T, but I get a completely different answer to what I need to show. Any help is really appreciated! Thanks so much. I'm not getting the book answer, either. Can you show what you are doing?

-Dan
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See the forum rules here.   Jul 11th 2014, 02:37 PM #3 Junior Member   Join Date: Jun 2014 Posts: 19 Ok so this is my working: F=ky => k= Fg/ y= 9.81x 1330/ 0.02= 652365 Nm-1 T= twopi square m/k= twopi square 1330/ 652365=0.2837 s f=1/T= 1/ 0.2837= 3.52 Hz (3 s.f) Is this the same answer you get? Thanks for your help.   Jul 11th 2014, 05:35 PM   #4
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 Originally Posted by Fizzle Ok so this is my working: F=ky => k= Fg/ y= 9.81x 1330/ 0.02= 652365 Nm-1 T= twopi square m/k= twopi square 1330/ 652365=0.2837 s f=1/T= 1/ 0.2837= 3.52 Hz (3 s.f) Is this the same answer you get? Thanks for your help.
Yup. We're on the same page.

-Dan
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See the forum rules here.   Jul 12th 2014, 02:09 AM #5 Junior Member   Join Date: Jun 2014 Posts: 19 Thanks for taking the time to help- it must just be a misprint in my textbook then.  Tags calculation, frequency 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 lynn Nuclear and Particle Physics 1 May 11th 2013 07:45 AM CCtree Advanced Mechanics 3 Apr 1st 2013 05:28 AM Devlan Thermodynamics and Fluid Mechanics 4 Aug 13th 2011 08:41 AM agentlopez General Physics 1 Feb 6th 2009 08:14 PM werehk Electricity and Magnetism 1 Jul 3rd 2008 05:14 AM