If I jump from a bus shall I be feeling the same force on my body as jumping from the train? Assuming both are running at same speed. I am asking this question because there is big difference between the mass of the train and the bus, does the mass of the moving body (in this case train/bus) will have any effect on the jumping body?
Well just considering speed, they should be both the same.
The speed you leave the train and bus is the same, so you have the same energy at impact, other things being equal.
The mass of the vehicle is irrelevant. It's the speed you leave with that counts.
On a practical note, trains tend to have doors significantly above track level compared to buses and roads. Buses have doors six inches or so above the ground. Trains have several feet of clearance between track and door.
So including this means you're likely to hit a little harder the ground from a train as you get more energy from the fall.
Of course if you're jumping onto the train station platform that difference disappears, because the train door is about about six inches above the platform, about the same as the bus and road separation.
However both forms of transport have something in common : they stop regularly. So wait for them to stop. :-)
Think of it in terms of change of momentum.
If you start with a certain momentum and finish with a certain momentum then the impulse on you has a certain value as impulse is equal to change in momentum.
So on the train/bus you start with a certain velocity which is the same for both vehicles and you then leave the train/bus with another velocity which is the same for both vehicles.
The change in your momentum is the same for both vehicles as is the impulse that the vehicle applies on you.
The impact occurs between the body and the ground. There is no contact with the train or bus when this impact occurs. So the mass of the train or bus is irrelevant.
If the body has the same speed and falls the same distance onto the same ground, the impact will be the same.
Here on earth there would be no difference you can feel between the bus and the train. Relative to earth's gravity your body's mass and velocity would be the same when you hit the ground. Think about the bowling ball and feather experiment, same falling speed, right? (Look it up if you don't know - its super cool)
But technically, and more to what you're maybe really asking, there is a VERY small difference. To understand the difference better let's change your thought experiment a bit , making the train something even bigger... let's say the size of earth. and instead of driving the bus down a road lets have it flying through space (to be fair to earth) Same question, is there a difference between jumping off a bus and jumping off earth? Well... yes obviously. The bus is small enough to leave you close to unaffected when you jump, you'll continue moving in the same direction modified by the force your legs exert in the separation (the bus's trajectory would also change a bit). Very different from your experience trying to jump from Earth. Earth is so big it's gravity field pulls you right back down. All mass comes with gravity, the bus and the train just aren't very different sizes and are surrounded by a much weaker gravity field than earth's strong gravity. Still our thought experiment shows that if we measured your landing point with a perfect microscope and kept zooming in we would eventually see (at a high enough magnification) that the train held you back ever so slightly - like sub-atomic slightly.
That said if this is an intro class you're asking about... best off saying it's the same.