You are Here: Home

# question on Q.I...fired gun-v-dropped bullet Tweet

Maths and statistics discussion, revision, exam and homework help.

Announcements Posted on
IMPORTANT: You must wait until midnight (morning exams)/4.30AM (afternoon exams) to discuss Edexcel exams and until 1pm/6pm the following day for STEP and IB exams. Please read before posting, including for rules for practical and oral exams. 28-04-2013
1. question on Q.I...fired gun-v-dropped bullet
From studying mechanics (some time ago, i`ll admit) i learned a lot of things, but i think this question on the Stephen Fry panel show Q.I. is so obviously untrue, i don`t know how they could try and pass it of as fact:

a person has a bullet in one hand and a loaded gun in the other .

He drops the bullet, and simultaneously fires the gun at the ground. from 1.5 metres.

Q.I.`s assertion is that both bullets will reach the ground at exactly the same time.

(these people are supposed to be intelligent, and have some intuition)

1) my intuition tells me that this answer is garbage!
2). so does the maths.

for the dropped bullet, you need the weight and the distance fallen.

research (t`internet) tells me that the average speed of a bullet from a handgun is approx 260 metres per second, so the answer Q.I. gives can`t possibly be correct!

(p.s. i can`t be bothered with the maths - i`ve been studying for the past 7 hours and iv`e got burnout)
Last edited by Hasufel; 09-07-2012 at 22:51.
2. Re: question on Q.I...fired gun-v-dropped bullet
Seems more like Physics than Maths but I think it's quite obviously true.
3. Re: question on Q.I...fired gun-v-dropped bullet
i`m not sure about the equations used to proove it, though!

i`d love to know the equations for seeing if it is true! Suvat?
4. Re: question on Q.I...fired gun-v-dropped bullet
i`ll try the math, thanks!
5. Re: question on Q.I...fired gun-v-dropped bullet
Get me two balls and a big tower. Also, a catapult.
6. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by Blazy)
Try throwing an object horizontally and dropping an object, both from same height.
This. See here.
7. Re: question on Q.I...fired gun-v-dropped bullet
QI is correct because they both fall from the same height of 1.5m, gravity acts on both in the same way and both bullets, for the example to work, weigh the same.

You're getting confused by the fact that one bullet is just being dropped (moving vertically due to gravity) and the other is being shot out of a gun (moving both horizontally due to the shot and vertically due to gravity).
8. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by Hasufel)
fires the gun at the ground. from 1.5 metres.
They didn't say that.
9. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by Hasufel)
From studying mechanics (some time ago, i`ll admit) i learned a lot of things, but i think this question on the Stephen Fry panel show Q.I. is so obviously untrue, i don`t know how they could try and pass it of as fact:

a person has a bullet in one hand and a loaded gun in the other .

He drops the bullet, and simultaneously fires the gun at the ground. from 1.5 metres.

Q.I.`s assertion is that both bullets will reach the ground at exactly the same time.

(these people are supposed to be intelligent, and have some intuition)

1) my intuition tells me that this answer is garbage!
2). so does the maths.

for the dropped bullet, you need the weight and the distance fallen.

research (t`internet) tells me that the average speed of a bullet from a handgun is approx 260 metres per second, so the answer Q.I. gives can`t possibly be correct!

(p.s. i can`t be bothered with the maths - i`ve been studying for the past 7 hours and iv`e got burnout)
Are you sure that you have worded the question correctly?

The gun must be horizontal when fired for it to be true. If the gun is pointing downwards then it is obviously not true.

Have a look here
10. Re: question on Q.I...fired gun-v-dropped bullet
Wouldn't the dropped bullet hit the ground marginally before the other one due to the curve of the Earth?
11. Re: question on Q.I...fired gun-v-dropped bullet
This is an amusing question because it comes to you in stages. When you are young you think obviously the dropped bullet will land first. When you get to highschool you learn Physics equations and realise that actually vertical and horizontal motion are independent of each other and so the bullets will land at the same time. When you think about it a bit more, though, you will notice that when you fire a bullet horizontally you are actually firing it away from the Earth and so it will land after the dropped one.
12. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by raheem94)
Are you sure that you have worded the question correctly?

The gun must be horizontal when fired for it to be true. If the gun is pointing downwards then it is obviously not true.

Have a look here
yes - they said that the fired one was fired at the ground!

(so they`re wrong?)
13. Re: question on Q.I...fired gun-v-dropped bullet
Wouldn't the caliber being used make a difference.
If the caliber is larger then wouldn't the heavier bullet and longer range change things?

I'm far too stupid to figure this out
14. Re: question on Q.I...fired gun-v-dropped bullet
The horizontal motion can be seen as unconnected to its vertical motion - this is basic M2 maths. The resultant force for the bullet in both cases is downwards (assuming no wind resistance). Hence, as they both start with a vertical velocity of zero, they will both fall at the same rate.

This is intuitive.
15. Re: question on Q.I...fired gun-v-dropped bullet
In the question does he fire the gun vertically or horizontally?
16. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by Hasufel)
From studying mechanics (some time ago, i`ll admit) i learned a lot of things, but i think this question on the Stephen Fry panel show Q.I. is so obviously untrue, i don`t know how they could try and pass it of as fact:

a person has a bullet in one hand and a loaded gun in the other .

He drops the bullet, and simultaneously fires the gun at the ground. from 1.5 metres.

Q.I.`s assertion is that both bullets will reach the ground at exactly the same time.

(these people are supposed to be intelligent, and have some intuition)

1) my intuition tells me that this answer is garbage!
2). so does the maths.

for the dropped bullet, you need the weight and the distance fallen.

research (t`internet) tells me that the average speed of a bullet from a handgun is approx 260 metres per second, so the answer Q.I. gives can`t possibly be correct!

(p.s. i can`t be bothered with the maths - i`ve been studying for the past 7 hours and iv`e got burnout)
Horizontal and vertical motion are independent. If the bullet it fired horizontally then it initially has no vertical speed and the only force acting on it in the vertical plane is gravity. Thus they both take the same amount of time to hit the ground.
17. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by Hasufel)
From studying mechanics (some time ago, i`ll admit) i learned a lot of things, but i think this question on the Stephen Fry panel show Q.I. is so obviously untrue, i don`t know how they could try and pass it of as fact:

a person has a bullet in one hand and a loaded gun in the other .

He drops the bullet, and simultaneously fires the gun at the ground. from 1.5 metres.

Q.I.`s assertion is that both bullets will reach the ground at exactly the same time.

(these people are supposed to be intelligent, and have some intuition)

1) my intuition tells me that this answer is garbage!
2). so does the maths.

for the dropped bullet, you need the weight and the distance fallen.

research (t`internet) tells me that the average speed of a bullet from a handgun is approx 260 metres per second, so the answer Q.I. gives can`t possibly be correct!

(p.s. i can`t be bothered with the maths - i`ve been studying for the past 7 hours and iv`e got burnout)
He doesn't fire the gun at the ground, he fires it horizontally.
(Well, that's what it's supposed to be, anyway. I don't know what they said on QI.)
Last edited by tazarooni89; 09-07-2012 at 23:48.
18. Re: question on Q.I...fired gun-v-dropped bullet
(Original post by Hasufel)
yes - they said that the fired one was fired at the ground!

(so they`re wrong?)
Can you please link me to the place where you saw it?
19. Re: question on Q.I...fired gun-v-dropped bullet
Yeah horizontally, they demoed this on one of the RI xmas lectures (using crossbow bolts) some years ago.
20. Re: question on Q.I...fired gun-v-dropped bullet
vertical speed is independent of horizontal speed (or so I was taught in physics.) So just because the bullet is moving at a great horizontal speed, it will still move at the same vertical speed as the bullet that is just dropped.