# Practical Daily question \[about jumping off a building\] **URL:** \ **Category:** Factual Questions\ **Created:** [May 11, 2009, 6:29pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068 "2009-05-11T18:29:40Z")\ **Posts on this page:** 20\ **Page:** 5
**Author:** ![zut](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/zut/32/2875_2.png) [@zut](https://boards.straightdope.com/u/zut)\ **Post date:** [May 19, 2009, 5:53pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/81 "2009-05-19T17:53:17Z")
> [@Shot\_From\_Guns](#): > > But… Why does the \*\*mass \*\*have anything to do with the air resistance? I can wrap my head around “more surface area equals more drag,” but I don’t get “more mass equals more drag.” Back up a second. More mass does _not_ equal more drag–in fact, the mass has no effect whatsoever on the drag _force_. But we’re not talking about the drag _force_, we’re talking about the _motion_ of the ping-pong ball–its position, velocity, and acceleration. I’m sure you’ll agree with the following equation: F = ma Now, if the force stays the same, and the mass _changes_, what happens to the acceleration? That’s what’s going on here–changing the mass doesn’t change the drag, it changes the _effect_ of the drag. ---
**Author:** ![Baracus](https://avatars.discourse-cdn.com/v4/letter/b/2bfe46/32.png) [@Baracus](https://boards.straightdope.com/u/Baracus)\ **Post date:** [May 19, 2009, 5:55pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/82 "2009-05-19T17:55:35Z")
> [@Shot\_From\_Guns](#): > > But… Why does the \*\*mass \*\*have anything to do with the air resistance? I can wrap my head around “more surface area equals more drag,” but I don’t get “more mass equals more drag.” It doesn’t, nor does it have to. The object with more mass has more downward force to overcome the air resistance. Imagine holding a balloon over your head and blowing upwards. The air resistance easily overcomes the weight of the balloon and propels it upwards. Now try to imagine doing that with the same balloon filled with water. ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [May 19, 2009, 5:56pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/83 "2009-05-19T17:56:32Z")
Perfect analogy, **Boyo Jim** , and thanks for the equation, **zut**. Got it now! ---
**Author:** ![Xema](https://avatars.discourse-cdn.com/v4/letter/x/9de053/32.png) [@Xema](https://boards.straightdope.com/u/Xema)\ **Post date:** [May 19, 2009, 6:08pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/84 "2009-05-19T18:08:47Z")
> [@Shot\_From\_Guns](#): > > [“In the absence of any other forces, any object will accelerate in a gravitational field at the same rate, regardless of the mass of the object.”](http://en.wikipedia.org/wiki/Gravitational_acceleration) As others have noted, the essential point is that other forces aren’t absent. In particular, aerodynamic drag is present. > [@](#): > > I don’t get “more mass equals more drag.” The important point is that more mass doesn’t equal more drag. The drag of a ping-pong ball is simply a function of its velocity (assuming its size and the air density are constant). More complete equations: If F = downward force, W = weight, M = mass, G = gravitational acceleration, D = drag and A = acceleration (actual change in vertical velocity), we can write: F = W - D W = M \* G F = M \* G - D F = M \* A A = F / M A = (M \* G - D) / M A = G - D/M From the final line we see that at any given speed, the greater the mass, the lower the acceleration penalty due to drag. ETA: Sorry - it took a long time for this to post. ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [May 19, 2009, 6:14pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/85 "2009-05-19T18:14:14Z")
Thanks, **Xema** –the problem was, I was picturing drag as a force acting equally on both objects and therefore might-as-well-be-absent. ---
**Author:** ![Hadrian\_s\_Wall](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hadrian\_s\_Wall](https://boards.straightdope.com/u/Hadrian_s_Wall)\ **Post date:** [May 23, 2009, 5:02am UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/86 "2009-05-23T05:02:43Z")
> [@HellsAngel21](#): > > That’s it. I cannot believe you. I cannot believe you. I thought I knew you. You have disappointed me majorly.:mad: You are now guaranteed that I will never make you any god damn food. Make it yourself! Oh honey! You know I love you! ---
**Author:** ![aldiboronti](https://avatars.discourse-cdn.com/v4/letter/a/9fc348/32.png) [@aldiboronti](https://boards.straightdope.com/u/aldiboronti)\ **Post date:** [May 23, 2009, 6:06am UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/87 "2009-05-23T06:06:52Z")
Well? Don’t keep us in suspense, OP. Did your friend hit her? ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [May 26, 2009, 8:44pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/88 "2009-05-26T20:44:29Z")
> [@McLuhan's Thunder](#): > > Oh honey! You know I love you! Not if it took you almost a week to reply, you don’t! 😃 ---
**Author:** ![Hadrian\_s\_Wall](https://avatars.discourse-cdn.com/v4/letter/h/58956e/32.png) [@Hadrian\_s\_Wall](https://boards.straightdope.com/u/Hadrian_s_Wall)\ **Post date:** [May 26, 2009, 9:56pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/89 "2009-05-26T21:56:50Z")
Sorry! Been alittle bit busy making up to the sweetest and most amazing woman in the world 🙂 ---
**Author:** ![HellsAngel21](https://avatars.discourse-cdn.com/v4/letter/h/9de053/32.png) [@HellsAngel21](https://boards.straightdope.com/u/HellsAngel21)\ **Post date:** [May 30, 2009, 8:06pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/90 "2009-05-30T20:06:52Z")
> [@McLuhan's Thunder](#): > > Sorry! Been alittle bit busy making up to the sweetest and most amazing woman in the world 🙂 Not if a certain someone keeps messing around on here when they should be studying:mad: then that woman ceases to be sweet. ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [June 1, 2009, 5:32pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/91 "2009-06-01T17:32:33Z")
Get a room, guys, we’re trying to employ the laws of physics in illegal and unethical ways here. ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [June 1, 2009, 6:57pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/92 "2009-06-01T18:57:19Z")
I dunno. From 600 feet away, I’m supposed to know when she’s exactly 26.2 feet from the impact point? I might need better glasses… ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [June 1, 2009, 7:25pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/93 "2009-06-01T19:25:32Z")
> [@mlees](#): > > I dunno. From 600 feet away, I’m supposed to know when she’s exactly 26.2 feet from the impact point? I might need better glasses… Well, I’m assuming the OP has some sort of system in mind to alert him when the woman in question passes the point where he should jump. Otherwise it would be silly to ask the question, wouldn’t it? ---
**Author:** ![mlees](https://avatars.discourse-cdn.com/v4/letter/m/ba8739/32.png) [@mlees](https://boards.straightdope.com/u/mlees)\ **Post date:** [June 1, 2009, 7:54pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/94 "2009-06-01T19:54:07Z")
> [@Shot\_From\_Guns](#): > > Well, I’m assuming the OP has some sort of system in mind to alert him when the woman in question passes the point where he should jump. Otherwise it would be silly to ask the question, wouldn’t it? We get all kinds 'round here. Never assume anything. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [June 1, 2009, 7:58pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/95 "2009-06-01T19:58:37Z")
> [@mlees](#): > > I dunno. From 600 feet away, I’m supposed to know when she’s exactly 26.2 feet from the impact point? I might need better glasses… How do figure this out is a separate thread. ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [June 1, 2009, 9:00pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/96 "2009-06-01T21:00:46Z")
The simplest way would be to just mark it out, have a spotter on the ground, and have the spotter let you know when she steps on the mark. Of course, you’ll have to compensate for any lag in the transmission. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [June 1, 2009, 11:25pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/97 "2009-06-01T23:25:26Z")
> [@Shot\_From\_Guns](#): > > The simplest way would be to just mark it out, have a spotter on the ground, and have the spotter let you know when she steps on the mark. Of course, you’ll have to compensate for any lag in the transmission. Yes, you’ll have to jump _just_ before the transmission. 😛 ---
**Author:** ![mwelch1904](https://avatars.discourse-cdn.com/v4/letter/m/d07c76/32.png) [@mwelch1904](https://boards.straightdope.com/u/mwelch1904)\ **Post date:** [June 2, 2009, 2:30am UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/98 "2009-06-02T02:30:22Z")
> [@AskNott](#): > > You’re going at this all wrong. Forget the 40 story building. Stand outside the classroom, and jump on her there. No need to go all superhero on her. Nobody meets cute by jumping off a building. Sheesh. Why, how clumsy of me to land on you… I was aiming for my car… Say, you have the most beautiful eyes, would you like to get some coffee sometime? How about 7:30 ish? Could you call an ambulance? Thanks ---
**Author:** ![Shot\_From\_Guns](https://avatars.discourse-cdn.com/v4/letter/s/ccd318/32.png) [@Shot\_From\_Guns](https://boards.straightdope.com/u/Shot_From_Guns)\ **Post date:** [June 2, 2009, 2:11pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/99 "2009-06-02T14:11:09Z")
> [@mwelch1904](#): > > Why, how clumsy of me to land on you… I was aiming for my car… Say, you have the most beautiful eyes, would you like to get some coffee sometime? How about 7:30 ish? Could you call an ambulance? Thanks I believe you meant, “Oh shiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiiii-- _ **GLORP** _.” ---
**Author:** ![Stan\_Shmenge](https://avatars.discourse-cdn.com/v4/letter/s/94ad74/32.png) [@Stan\_Shmenge](https://boards.straightdope.com/u/Stan_Shmenge)\ **Post date:** [June 2, 2009, 2:37pm UTC](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068/100 "2009-06-02T14:37:40Z")
I thought homework questions in Physics 101 usually allowed you to ignore air resistance… [Previous page](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068.md?page=4) [Next page](https://boards.straightdope.com/t/practical-daily-question-about-jumping-off-a-building/496068.md?page=6)