Effect of Air Resistance on the Speed of a Thrown Ball

[sammyj]

I understand that in the absence of air resistance, if a ball is thrown vertically upward with a certain initial speed, on returning to its original level it will have the same speed.

But when air resistance is a factor, will the ball be moving faster, the same or more slowly than its throwing speed when it gets back to the same level?

I believe it will move more slowly. But why does air resistance cause this?

 

[mgb_phys]

Conservation of energy.
You give the ball a certain amount of kinetic (motion) energy when you throw it.
If no energy is lost then it will return to the same point with the same energy and so the same speed.
Air resistance uses up some of the energy (it actually heats the air - difficult to measure with a ball but imagine the space shuttle re-entering the atmosphere!) so the ball returns with less speed.

 

[sammyj]

aahh gotcha. Thank you for breaking that part down.