# B Falling question about terminal velocity

1. May 26, 2017

### Robertmunch

Hey guys I have a question.

Terminal velocity is 9.81mps correct? Which converts to basically 35kmph so does that mean hitting the ground from free fall after jumping out of an air plane would have the same effect as hitting a wall or something immobile and hard at 35kmph?

Thanks

2. May 26, 2017

### restart

Terminal velocity is not 9.81 m/s, it is the acceleration due to gravity that is 9.81 m/s^2. The terminal velocity acquired depends on the weight that is falling out of the airplane.
But in the case that there is some arbitary object with terminal velocity 9.81 m/s, the effect of having it fall to the ground and having it collide with an immobile wall, will be the same; the momentum imparted will be 9.81×mass in both cases.

3. May 27, 2017

### Robertmunch

Oh I had a brain fart I guess. I thought I remembered a demonstration from physics class where the teach dropped 2 objects of different mass and they both hit the ground at the same time (obv the shape of the object would make a difference because of air resistance)

4. May 27, 2017

### Janus

Staff Emeritus
The experiment was to demonstrate that all objects (at the same distance above the Earth's surface) will fall at the same rate regardless of their mass, assuming that you can neglect air resistance. Objects are chosen so than the effect of air resistance is negligible over the fall.
Terminal velocity occurs when air resistance comes into play. It is determined by the the relationship between an object's size, shape and mass. Air resistance increases with velocity, so as the falling object accelerates, the air resistance increases, at some point the air resistance equals the force of gravity trying to accelerate the object, it has reached terminal velocity and just continues to fall at a set speed. Because of the above mentioned factors, terminal speeds for various objects can vary greatly. ( the terminal speed for a ball bearing will be greater than that of a feather even if they had the same mass).