Physics Question

[WolfLMM]

A bullet is fired straight up into the air, stops breifly, and falls back to earth. When is the bullet accelerating?

 

[Kat]

Pat says always because deceleration is actually an acceleration.

 

[SSchmi5519]

It is always. All changes in movement are acceleration, even slowing down or changes in direction.

 

[paint94979]

Always

 

[WolfLMM]

Dang, Ya'll are good.:thumb: I tripped up a lot of college students today with that question.

 

[Chevy1925]

damn it! got that it was decerating on its way up but totally forgot either way was a form of acceleration, been out of school for a year and im already forget crap

 

[smarquis]

I don't think that answer is correct. After the bullet starts falling back to the ground, it will quickly hit its terminal velocity (maximum velocity reachable given the wind resistance), and it will stay at that velocity until it hits the ground. Thus, the bullet will only be accelerating during most of the flight. Am I wrong?

 

[Mike L.]

Then why was the word de accelerate invented? The bullet will accelerate about a hundred yards from the barrel then de accelerate, which means slow down. It no longer accelerates.

 

[SSchmi5519]

Acceleration-Any change in velocity.

 

[dbenenh0]

It will always be accelerating. We talked about this in my physics I class last semester

 

[dieselson]

Its always accelerating because like kat said, even deceleration is acceleration. I guess it helps that im taking physics in school right now

 

[SBLC]

I don't think that answer is correct. After the bullet starts falling back to the ground, it will quickly hit its terminal velocity (maximum velocity reachable given the wind resistance), and it will stay at that velocity until it hits the ground. Thus, the bullet will only be accelerating during most of the flight. Am I wrong?

Its a physics problem so you have to make assumptions that it never hits terminal velocity this is an ideal bullet we are talking about:spit:.

Kidding aside, the bullet will have zero acceleration at that split second it has reached its maximum height before accelerating down.

 

[dieselson]

Its a physics problem so you have to make assumptions that it never hits terminal velocity this is an ideal bullet we are talking about:spit:.

Kidding aside, correct me if Iam wrong but wont the bullet have zero acceleration at that split second it has reached its maximum height before accelerating down.

No matter what gravity is always acting on it causing it to accelerate, at a rate of 9.8 m/s/s whether it is making the bullet slow down or speed up.

 

[paint94979]

No matter what gravity is always acting on it causing it to accelerate, at a rate of 9.8 m/s/s whether it is making the bullet slow down or speed up.

x2

I considered that the bullet might reach terminal velocity but you have to assume it never does

editL SBLC beat me too it

 

[dieselson]

Funny thing is, I actually took a test on this exact subject today :rofl:

 

[smarquis]

It is a bullet shot straight up on a planet with no atmosphere. LOL. :beer

 

[SBLC]

No matter what gravity is always acting on it causing it to accelerate, at a rate of 9.8 m/s/s whether it is making the bullet slow down or speed up.

Gravity is always pointing down(-g) which is why the bullets acceleration is getting smaller(for some de-acceleration). Then the acceleration of the bullet is zero(for a infinitesimally small amount of time), then it accelerates down.
acceleration=(change in velocity)/(change in time). So on a graph of velocity vs time the slope ([rise/run], [change in velocity/change in time]) is the acceleration. Thats my thinking:hug:

 

[minisub]

No matter what gravity is always acting on it causing it to accelerate, at a rate of 9.8 m/s/s whether it is making the bullet slow down or speed up.

Please tell me that schools are really teaching that the force of gravity is 32 ft/s/s and you made the conversion yourself.....

Now what if the bullet was fired on a conveyor belt....

 

[WolfLMM]

Its a physics problem so you have to make assumptions that it never hits terminal velocity this is an ideal bullet we are talking about:spit:.

Kidding aside, the bullet will have zero acceleration at that split second it has reached its maximum height before accelerating down.

Wrong. If that were true the bullet would float in mid air

 

[WolfLMM]

It is a bullet shot straight up on a planet with no atmosphere. LOL. :beer

It's an elementary physics question no need to get hung up on air resistance.