## arcticf0x 3 years ago Projectile motion

1. arcticf0x

let me draw it out

2. JamesJ

Ah @eashmore is here. He eats these problems like popcorn at a movie.

3. eashmore

Only if the butter isn't too thick!

4. arcticf0x

its not a problem, its just one stupid question, i am not able to draw properly with this editor lol

5. JamesJ

Draw a picture, take a picture of it and upload it. I do that all the time. Let us know when you're ready

6. arcticf0x

yep! one second

7. arcticf0x

My question is, will the time from O to P will be equal to P to S when there is air drag?

8. arcticf0x

Popcorn! lol

9. JamesJ

No, it is not. Classic question in kinematics. And why not?

10. arcticf0x

But the trajectory is different from P to S right? so why not?

11. JamesJ

On the way up to the top of it's trajectory, there are two forces acting: gravity and air resistance. Air resistance of course is always in the direction of -v, the velocity vector. Air resistance has negative y component and gravity is in the negative y direction. On the way down, the air resistance has positive y component and hence the net force in the y direction is less than on the way up. The result is the magnitude of the force on the object on the way up is more than it is on the way down. So the time required to reach the top of its trajectory is created than the time required for it to travel from the top to the bottom.

12. JamesJ

To convince yourself of this, take a large piece of paper, like a newspaper. Crumble it up into a rough ball. Throw it up and notice it takes less time to reach the top of its trajectory than it does to come down.

13. arcticf0x

Nah, i understood it from, when i serve in tennis, it takes more time to go up but land a bit faster in the box! Gravity and air restistance! I always liked the symmetry for projectiles until yesterday i watched this lecture on air drag! Thanks a lot @JamesJ !!!!

14. arcticf0x

lands*

15. eashmore

This effect is most noticeable on the smaller curves.

16. arcticf0x

Oh ok!

17. arcticf0x

/offtopic Lets make it 1000 medals tonight @JamesJ ! :D

18. JamesJ

?

19. arcticf0x

20. arcticf0x

haha leave it if you dont care :P

21. JamesJ

Ah! I haven't looked at that number for a long time. Yes, why not? ;-)