# B Slope acceleration vs mass

1. Mar 15, 2016

### saucemoss

Hi,
Im on a sking trip with 6 od my friends and they all say thathat a heavier skieer caches up on speed on slope faster than lighter one, (no matter the volume od the ski person). Im saying that mass od the skier does not matter, but the won't listem to me. Am I wrong and crazy? IF im right, how can I explain it to them? Please help
Bregards

2. Mar 15, 2016

### ProfuselyQuarky

No, heavier skiers go down faster because air resistance (drag) has a lesser affect on them. They also have more momentum. Oh, and you also have to account for the snow's friction. Once you add up all these factors, you'll find that the mass of the skier does, in fact, change the person's velocity.

3. Mar 15, 2016

### ProfuselyQuarky

That's correct if you're in a vacuum (no air), since nothing like air resistance exists in a vacuum. However, skiing down a slope is much to the contrary.

Last edited: Mar 15, 2016
4. Mar 15, 2016

### A.T.

Assuming all skiers have the same density, drag and friction coefficients, that is correct.

Only if you also ignore air drag.

5. Mar 15, 2016

### saucemoss

When you drop two balls that have the same volume but different mass from any height they will be accelerated at the same rate since gravity acceleration is the same. They will fall at the same time. Air drag is the same because the volume is the same. where is the difference when I introduce slope? Only force that is accelerating skiier is gravity. What don't I understand? :(

6. Mar 15, 2016

### A.T.

Not in air.
Same drag & Different weight -> Different net force to mass ratio -> Different acceleration

Last edited: Mar 16, 2016
7. Mar 15, 2016

### ProfuselyQuarky

Yep, you're right. Since the acceleration due to gravity is the same for all objects, all objects regardless of mass, would fall at the same rate in a vacuum. Air resistance is not the same for all objects because the affects that drag has on an object is proportional to the mass (and even shape) of the object. And, like how I said before, there are other factors involved. If you drop a flat sheet of paper at the same time as a crumpled sheet of paper, which do you think will fall first?

8. Mar 16, 2016

### saucemoss

I get it now. Thanks for answers :)

9. Mar 16, 2016

### ProfuselyQuarky

Have fun for the remainder of your ski trip!