Physics Question---F=ma?

[Lucifer]

Take a mass of 100 grams, and gravity's acceleration, 9.81m/s^2.

Let's say you drop the 100g object from a building
If F=ma, does that mean that the 100g object hits the ground with the same force, no matter how high you drop the object from? Because m is always 100g, and gravity is always 9.81m/s^2?

[Raen]

You're correct in your implied assumption that that conclusion doesn't make sense.

When things accelerate, they speed up. The longer it falls, the faster it gets.

When it hits the ground, it has to stop, and to do this, it decelerates, or has negative acceleration.

That is the acceleration that's important in calculating the force.

Example: a 10kg object is dropped from a certain height, so that at the instant before it hits the ground, it's going 50 m/s.
Same size object, dropped right above the ground is only going 10m/s when it hits. So they'll decelerate at different rates when they hit, changing the A in the equation. I
If two objects are dropped from different heights that are both really high, they'll reach terminal velocity, when they won't accelerate any more, and they'll hit at the same speed, so F will be the same.