Projectile Motion Question....HELP PLEASE!!!

[Lawliet2008]

If you consider air resistance, does a projectile take longer to ascend or descend?

Why?

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[BloodySurgeon]

If you consider air resistance, does a projectile take longer to ascend or descend?

Why?

descend

mg + air resistance = ma (going up)

mg - air resistance = ma (going down)

 

[wannabedocta]

If you consider air resistance, does a projectile take longer to ascend or descend?

Why?

Yea think about a large feather descending versus a penny of the same mass falling. The feather has a larger surface area and larger air resistance so it would take longer to descend.

 

[canjosh]

If you consider air resistance, does a projectile take longer to ascend or descend?

Why?

Is the question comparing time for ascent versus time for descent? Or is it just asking what effect wind resistance has on projectile motion? If it is the latter, then of course air resistance increases time for both ascent and descent because resistance is acting opposite the motion. However, if the question is asking which takes longer, I would have to say that ascent and descent are equal. The path should be symmetrical unless winds are changing throughout the flight. The object has the same mass and surface area throughout the flight, and gravity is constant. Unless I'm missing a concept here or something...

 

[iA-MD2013]

Is the question comparing time for ascent versus time for descent? Or is it just asking what effect wind resistance has on projectile motion? If it is the latter, then of course air resistance increases time for both ascent and descent because resistance is acting opposite the motion. However, if the question is asking which takes longer, I would have to say that ascent and descent are equal. The path should be symmetrical unless winds are changing throughout the flight. The object has the same mass and surface area throughout the flight, and gravity is constant. Unless I'm missing a concept here or something...

I think I agree with you...air resistance always acts against motion. Why did you add the air resistance on the ascend, BloodySurgeon?

 

[physics junkie]

This is actually a problem in the feynman lectures on physics. The solution can be seen here: http://feynmanlectures.info/exercises/ball_up_down.html

http://feynmanlectures.info/solutions/ball_up_down_sol_2.pdf is the solution that is readable for people who haven't taken differential equations.

It turns out the ball takes longer coming down because when the ball is going up air resistance and acceleration due to gravity both point in the same direction but when the ball is coming down the forces point in opposite directions. This is what bloodysurgeon said.

 

[iA-MD2013]

This is actually a problem in the feynman lectures on physics. The solution can be seen here: http://feynmanlectures.info/exercises/ball_up_down.html

http://feynmanlectures.info/solutions/ball_up_down_sol_2.pdf is the solution that is readable for people who haven't taken differential equations.

It turns out the ball takes longer coming down because when the ball is going up air resistance and acceleration due to gravity both point in the same direction but when the ball is coming down the forces point in opposite directions. This is what bloodysurgeon said.

ohh ****...yeah! thanks (again) phys junkie!

 

[tncekm]

edit: too late