Hello everyone, I was doing some experiment using a spring compressed gun, that shoots up ball beraings. I made it using a desoldering pump and a PVC pipe,its quite small. ok, so I set it in 45° angles for maximum range. A desoldering pump has a spring inside, when you push down on top the spring compresses and stays compressed until you click on the button which releases it. This force of the spring getting released exerts a force on the ball bearing causing it to launch into the air. so, i used different bearing balls with same diameter but different weights. The force exerted by the gun is the same so I thought the initial velocity is constant. But later i found Newton's 2nd law stating F=ma so if F is constant, and mass is increased, 'a' will change resulting in a change in Initial velcoity (Vi) beacuse, a=(Vf-Vi)/t so later i found hooke's law F=kx F=ma a=(vf-vi)/(tf-ti) putting them all together i got an equation to find the initial velocity of a projectile -vi=(kχx/m)(t)-Vf where, k is the spring constant(which i found) , x is the displacement of spring due to compression(which i can see) and time(i used a stopwatch) and vf is zero as it is the maximum point of proejctile. ok so i worked it out for each mass of ball bearing and got Vi for four ball bearings which were all the same (6m/s). Can some one check if this equation and the way I am doing this is right beacuse when u use the same intial velcoity for launching a ball aren't all the ball bearings suppposed to land in the same position and have the same flight time. But, when I did the actual investigation, the time were different and the distance were different too . I am totally going paranoid with this problem . some one please help me! its due in 3 days and I am not even half way through. please help me :( :( :( :( Thank u so much for your help!!!!!!!!!!!!!