Effect of mass on kinematics?

[nejikon]

I honestly am so confused because from what I learned mass has no impact on the outcome of projectiles as two are launched they should land at the same time. Some questions, however, say that the heavier one will fall earlier and first. So, what is the consensus on this?

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[aldol16]

If they are both dropped vertically from rest or with the same velocity, they must necessarily land at the same time. delta y = v0*t + 0.5*g*t^2. Therefore, t only depends on v0 and height, neither of which are dependent on mass. Since everything experiences the same acceleration due to gravity, the center of mass motion is not dependent on mass.

However, the force of gravity acting on a heavier object is greater, as given by F = m*g. Further, drag will have an effect if you don't assume negligible air resistance and it could be that some heavier objects will land first because they experience less drag. For instance, compare a marble and a piece of paper of the same mass. In that case, gravity is no longer the only force - the air particles hitting the cross-sectional area of the object exert a non-negligible pressure and thus force on the object, causing a less-than-expected acceleration.

 

[Cawolf]

 

[NextStepTutor_2]

long story short, if gravity is the only force then yes, mass is irrelevant. Once other forces (friction, air res, etc..) comes into play, mass will matter.

good luck!