# Motion in one dimension

by ranjitnepal
Tags: dimension, motion
 P: 6 when we throw an object upwards why the time of descent is greater rhan time of ascent?
 P: 327 It's not. The object's descent is just a time-reversed ascent, because total energy is conserved.
Mentor
P: 3,903
 Quote by ranjitnepal when we throw an object upwards why the time of descent is greater rhan time of ascent?
What specific situation are you considering? In general, the two times will be about the same, with any difference being caused by air resistance acting differently on the ascent and the descent.

 P: 6 Motion in one dimension in case we consider air resistance
Math
Emeritus
Thanks
PF Gold
P: 39,682
 in case we consider air resistance
Don't you think it would have been a good idea to tell us that initially?

The speed coming down will be less than the speed going up because the potential energy will be the same at the same height but the total energy will be less because of energy lost to air resitance. So kinetic energy will be less at the same height coming down than going up.
Mentor
P: 3,903
 Quote by ranjitnepal in case we consider air resistance
Even then, the details matter. A dense sphere (think cannonball) with an initial speed of a few tens of meters per second will not be measurably affected by air resistance - and this is also the problem you'll most often encountered in introductory physics classes. On the other hand, a spin-stabilized projectile that tumbles on the the way down, or a projectile whose initial velocity exceeds its terminal velocity in air will behave very differently on ascent and descent.

 Related Discussions Introductory Physics Homework 3 Introductory Physics Homework 1 Introductory Physics Homework 3 Introductory Physics Homework 2 Introductory Physics Homework 2