# How do I applied the acceleration load to point mass in Calculix **URL:** \ **Category:** Uncategorized\ **Created:** [November 23, 2023, 6:21am UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933 "2023-11-23T06:21:40Z")\ **Posts on this page:** 10\ **Page:** 1
**Author:** ![osmcnkrtn](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/osmcnkrtn/32/2491_2.png) [@osmcnkrtn](https://calculix.discourse.group/u/osmcnkrtn)\ **Post date:** [November 23, 2023, 6:21am UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/1 "2023-11-23T06:21:40Z")
![mass_accelerate](https://global.discourse-cdn.com/free1/uploads/calculix/original/2X/b/b378abfd36f261539ebb709a9ed9620894469892.png) I have a model where I apply an acceleration to a point mass and I’m trying to observe the reaction force values in solid models. I used the following code for the model. However, I’m not sure if the mass element is properly receiving the acceleration load. When I change the mass within the \*Mass element, the results vary, but I still think the reaction force is coming out too low. Is there an additional card I should be using in my code? Should I incorporate the gravity constant? Here’s the part of the code I wrote. \*Node 17852, 100, 100, 100 17853, 100, 100, 100 \*ELEMENT, TYPE=MASS, ELSET=mass 999999, 17852 \*MASS, ELSET=mass 0.01 \*Rigid body, Nset=fix1, Ref node=17852, Rot node=17853 \*DLOAD mass,GRAV,9800,-1.5,0.,-4. ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [November 23, 2023, 8:11am UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/2 "2023-11-23T08:11:40Z")
> [@osmcnkrtn](#): > > but I still think the reaction force is coming out too low What is it and what would you expect it to be ? How do you read it ? ---
**Author:** ![osmcnkrtn](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/osmcnkrtn/32/2491_2.png) [@osmcnkrtn](https://calculix.discourse.group/u/osmcnkrtn)\ **Post date:** [November 24, 2023, 9:12am UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/3 "2023-11-24T09:12:55Z")
Hi Calc\_em, I read it from Rf node output. For an example case, reaction forces differs 10N with respect to analytical solution. I expect 50N but i got 40N. The error is about 25 percent which is very high? Additionally, is it the true definition of applying acceleration on two direction? \*DLOAD mass,GRAV,9800,-1.5,0.,-4. Should i define it like in two rows for applying acceleration on both x and z direction? mass,GRAV,9800,-1.5,0.,0. mass,GRAV,9800,0.,0.,-4. I try to apply 4g acceleration on z axis and at the same time apply -1.g acceleration on x axis. ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [November 24, 2023, 11:45am UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/4 "2023-11-24T11:45:06Z")
Could you share the full inp.? ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [November 24, 2023, 12:03pm UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/5 "2023-11-24T12:03:23Z")
> [@osmcnkrtn](#): > > I try to apply 4g acceleration on z axis and at the same time apply -1.g acceleration on x axis. I guess that you mean -1.5g for x. In such a case, PrePoMax generates: ```auto *Dload Internal_Selection-1_Gravity-1, Grav, 41908.3383707825, -3.51123442E-001, 0, 9.36329178E-001 ``` Internally, PrePoMax calculates the resultant acceleration and adds its magnitude and direction to the input file. ---
**Author:** ![osmcnkrtn](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/osmcnkrtn/32/2491_2.png) [@osmcnkrtn](https://calculix.discourse.group/u/osmcnkrtn)\ **Post date:** [November 25, 2023, 2:00pm UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/6 "2023-11-25T14:00:07Z")
Are we sure about the accuracy of Prepomax in calculating the correct vector? How does Prepomax perform this calculation? Would it be incorrect if I define acceleration in the x-direction as 1.5g and in the z-direction as 4g like this? \*DLOAD mass,GRAV,13700, 1,0.,0. mass,GRAV,39200,0.,0.,1. ---
**Author:** ![osmcnkrtn](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/osmcnkrtn/32/2491_2.png) [@osmcnkrtn](https://calculix.discourse.group/u/osmcnkrtn)\ **Post date:** [November 25, 2023, 2:00pm UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/7 "2023-11-25T14:00:45Z")
Actually rest of the code is \*Node and same things . Nothing more than this ---
**Author:** ![Disla](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/disla/32/3548_2.png) [@Disla](https://calculix.discourse.group/u/Disla)\ **Post date:** [November 25, 2023, 2:19pm UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/8 "2023-11-25T14:19:46Z")
Check signs. > **[How to Normalize a Vector: 9 Steps (with Pictures) - wikiHow](https://www.wikihow.com/Normalize-a-Vector)** > > A vector is a geometric object that has direction and magnitude. It may be represented as a line segment with an initial point (starting point) on one end and an arrow on the other end, such that the length of the line segment is the... ---
**Author:** ![Calc\_em](https://avatars.discourse-cdn.com/v4/letter/c/43a26b/32.png) [@Calc\_em](https://calculix.discourse.group/u/Calc_em)\ **Post date:** [November 25, 2023, 2:25pm UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/9 "2023-11-25T14:25:31Z")
> [@osmcnkrtn](#): > > Are we sure about the accuracy of Prepomax in calculating the correct vector? Don’t worry about that. Abaqus generates the same: ```auto *Dload , GRAV, 41908.3, -0.351123, 0., 0.936329 ``` ---
**Author:** ![osmcnkrtn](https://yyz2.discourse-cdn.com/free1/user_avatar/calculix.discourse.group/osmcnkrtn/32/2491_2.png) [@osmcnkrtn](https://calculix.discourse.group/u/osmcnkrtn)\ **Post date:** [November 25, 2023, 2:31pm UTC](https://calculix.discourse.group/t/how-do-i-applied-the-acceleration-load-to-point-mass-in-calculix/1933/10 "2023-11-25T14:31:05Z")
[quote=“osmcnkrtn, post:6, topic:1933”] Thanks Calc\_em and Disla. I think we can close this task. Thank you for your help.