# Falling from a mountain

1. Nov 19, 2013

### Hepic

Lets say that I am falling down from a mountain. Then only thing that I have with me is a big stone. Lets say that when I have distance 50m from the ground,I put the rock down of my legs,and I jump(hitting my legs at stone). If my speed was 100 m/s,will decrease after jumping or that is impossible?

Thanks!!!

2. Nov 19, 2013

### Staff: Mentor

You exert a force on the stone, the stone exerts a force back on you. These forces will affect the acceleration of you and the stone. How do you think it will turn out?
(Yes, I understand that you wouldn't be asking if you KNEW what would happen... but what do you THINK will happen?)

3. Nov 19, 2013

### Khashishi

4. Nov 19, 2013

### gabriel.dac

lol I used to ask myself this question all the time when I was younger.

The short answer no, you will still probably die. Unless your legs are really really strong and can cancel earth's acceleration

5. Nov 20, 2013

### BruceW

yeah, you'd need to throw down the rock with a ridiculous amount of force. In reality, it would probably be better to just free-fall alone, because if you are holding on to the rock, getting ready to throw it, then you will be moving down at faster than the free-fall speed of an isolated person. But in either case, your chances are not good.

6. Nov 20, 2013

### MikeGomez

What would be the reason for that? Air resistance?

7. Nov 20, 2013

### BruceW

yeah, that's what I meant. (sorry I didn't really explain). Since I'm guessing a rock is more dense than a human. yeah, even if the human is approximately the density of water, a big rock is not going to float in water, so the rock should definitely be more dense than the human.

So, does that mean that if you were falling alongside an iceberg, you should hold on to the iceberg so that it gives you a slower terminal velocity? haha. I guess also the shape of the object makes a difference, for example a human can spread his arms and legs out to slow himself down slightly.

8. Nov 20, 2013

### jbriggs444

At the risk of continuing the digression...

Density is not quite the right figure-of-merit. Yes, shape matters. And orientation. For instance, an arrow falls faster if you put feathers on one end so that it stays vertical. One simple model is that drag is proportional to cross-sectional area. This is multiplied by a fixed factor which depends on shape and is known as the "drag coefficient". So even though an iceberg may not be dense, it will have a high mass to cross-section ratio. So it will fall fast.