calculation max load on a scissor jack lifting a carby vpatel28 Tags: engineering, mechanical, physics, scissor jack 

#1
Nov709, 10:24 PM

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1. The problem statement, all variables and given/known data
I have to determine the max load a scissor jack must support when lifting a 6000lb car. I know where the center of gravity is acting and the potential locations (distances from the center of gravity) the car will be jacked up. I know the max force is less than 6000 lb. 2. Relevant equations 3. The attempt at a solution I tried taking the moments about one of the tires and setting them equal to zero to solve for the max force at each location, but I know I'm doing something wrong. 1. The problem statement, all variables and given/known data 2. Relevant equations 3. The attempt at a solution 



#2
Nov809, 06:41 AM

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Hi vpatel28! Welcome to PF!
show us what you got! 



#3
Nov809, 10:47 AM

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I've attached a diagram of the geometry of the car. The more I think about the problem, I feel like I need to know which two tires the car will lean on for each case. Inspection tells me that it will lean on the two side tires for both cases.
Do I want to take the moment about one of the tires that car is leaning on? If I do that I get the following: Case 1  Lean on Back wheels (6000)(8 ft) + F(10) = 0 F= 4800 lb Case 2  Lean on Side Wheels (6000)(3) + (F)(6) = 0 F = 3000 lb I'd appreciate any help in directing me in the right direction 



#4
Nov809, 11:40 AM

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calculation max load on a scissor jack lifting a carbut that certainly looks ok! 



#5
Nov809, 12:16 PM

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Sorry about that. Here is the attachment with the diagram




#6
Nov809, 02:19 PM

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The jack points are 2ft behind or in front of the nearest wheel. The c.o.m. is 4ft behind the front wheels and 8ft in front of the back wheels. 



#7
Nov809, 02:25 PM

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If the the car leans on the side wheels for both cases then isn't the max force the same in both cases?



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