Finding Force to Accelerate a Wheel Cart for Bending Moment Calculation

[1988ajk]

I am having trouble trying to find the force required to accelerate a wheeled cart. so that i can calculate the bending moment in a stopping bracket,

the bit I am stuck on is The Acceleration of the cart, the situation is;

An 80,000Kg Wheeled cart runs on rails from rest and hits a stop after 7.8m at a velocity of 0.1m/s

what is the acceleration of the cart at 7.8m?,

this would allow me to find the force F=MA

I would be very grateful for your input,

*Note, this is not a homework question


Adam.

 

[Naty1]

d = 1/2at.t is one relationship to get a.

But you do NOT need that to determine the stopping force. All that matters at the moment of impact is the velocity (momentum) of the cart.

F =ma is NOT the relationship you think on the stopping side ...The "a" there would be the deceleration experienced and has nothing to do with the "a" that caused the cart to accelerate in the first place...

Try an approach like FT= MV for stopping force...you'll have to decide how long that fixed constant force "F" acts..pick a "T" during which time the cart stops...say 0.1 or 0.01 seconds or whatever you like. And recognize that because the cart may crumple..deform...upon impact, the force is not really constant...

 

[Naty1]

formula above is supposed to be d = 1/2at²

 

[1988ajk]

thanks for that,

however I think I haven't put enough detail into my problem. to find the impact stress I am using an expression from the Roark book on stress and strain where the impact stress can be calculated from a theoretical static stress.

this is the reason I was interested in the acceleration. If I use the expression for acceleration you gave, putting in time taken for the bogie to reach the stop from rest, will this value be able to be used to find the force to push the cart. F=ma