- #1

jshaner858

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If so please give examples. I asked my TA this question today and she did not know the answer...? Help!

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- Thread starter jshaner858
- Start date

- #1

jshaner858

- 20

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If so please give examples. I asked my TA this question today and she did not know the answer...? Help!

- #2

yourdadonapogostick

- 270

- 1

velocity will increase if acceleration is still positive

- #3

jshaner858

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- #4

yourdadonapogostick

- 270

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yes, as long as a is still positive

- #5

jshaner858

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- #6

yourdadonapogostick

- 270

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- #7

jshaner858

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- #8

yourdadonapogostick

- 270

- 1

nah, you're still increasing

- #9

LURCH

Science Advisor

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At 4 G's, you might look at your ground-speed indicator and see that, for every second you continue that burn, you go almost 130f/s faster than you were going the previous second. As you throttle back through 2G's, you'll see that you only gain 64f/s for every second you stay at that setting. And when you ease it down to 1G, you'll notice that you're going 32f/s faster for every second you coninue. Yet, even at 1G, you're still accelerating (@32f/s).

So, your magnetude of acceleration has decreased from 4G's through 3 and 2, to 1G, but you were allways accelerating. You just started out accelerating hard, and ended up only accelerating a little.

'Zat make any sense?

- #10

Doc Al

Mentor

- 45,447

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No. Assuming straight line motion, when your acceleration is 2 m/s^2 it means that yourjshaner858 said:when you accelerate 2 m/ss both speed and accel are increasing,

Be careful with directions and signs though. It may be that your

Don't say "slow down" when talking aboutbut when you slow down by 1 m/ss then your speed and accel are both decreasing...??

If your acceleration changes from 2 m/s^2 to 1 m/s^2, then you are still speeding up! Just not as quickly. Only when the acceleration goes to zero do you stop accelerating. If it goes

- #11

reilly

Science Advisor

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Regards,

Reilly Atkinson

- #12

jshaner858

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So the answer is NO, because if you decrease acceleration from 10 to 1, you are still increasing your speed, but your acceleration is decreasing?

- #13

krab

Science Advisor

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if you decrease acceleration from 10 to 1, you are still increasing your speed, but your acceleration is decreasing?

This is a situation of very common occurrence. Anytime you hit the accelerator in a car, you will accelerate, but because of aerodynamic drag, this acceleration decreases as speed increases.

Last edited:

- #14

yourdadonapogostick

- 270

- 1

if you mean absolute value as in [tex]|\vec{v}|^2=\sum_{j=1}^{n}a_j^2[/tex] where n is the number of dimensions of the space in which the vector exists, and a is the coefficient of the unit vector in a given dimenson, then yes, it does have an absolute value. magnitude is always positive. the direction isn't, though. when in one dimension(like your example) it is convenient to use a - sign instead of assigning an angle.jshaner858 said:

So the answer is NO, because if you decrease acceleration from 10 to 1, you are still increasing your speed, but your acceleration is decreasing?

- #15

Doc Al

Mentor

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Not sure what you mean. Magnitude of acceleration is the value of the acceleration regardless of direction or sign.jshaner858 said:Doc Al, I think I understand the way you put it, however, does the word "magnitude" not imply an "absolute value" for acceleration?

I'm not sure what question you are referring to. If your question is the one you raised in your first post ["Is it possible to have an INCREASING speed AND have the MAGNITUDE of acceleration decreasing?"], then the answer is a big YES. My point was that (assuming the velocity and acceleration are in the same direction)I have been leaning toward YES as being the answer to my question, but you saying NO has thrown me for a loop.

I'm not sure what question is getting the NO answer, but your statement is completely correct. An acceleration of 10 m/s^2 or 1 m/s^2So the answer is NO, because if you decrease acceleration from 10 to 1, you are still increasing your speed, but your acceleration is decreasing?

- #16

reilly

Science Advisor

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Regards,

Reilly Atkinson

- #17

njmorin

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- #18

GRDixon

- 249

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If so please give examples. I asked my TA this question today and she did not know the answer...? Help!

A mass on a spring. Note that the following is also true (at appropriate times in an oscillation): the speed can be DECREASING while the MAGNITUDE of the acceleration is INCREASING.

- #19

njmorin

- 2

- 0

Acceleration and deceleration are changes in speed, and the rate of those measured in G's. 1G is the rate of acceleration in free fall relative to the force of Earth's gravity(pull force) at sea level. So I can go from 1 to 2 mph at 1g in a certain amount of time at acceleration value x or in twice that time at acceleration value x/2. In both cases my speed is increasing to 2 mph, it just takes twice as long to get to that speed at half the acceleration. Clear as mud? I just did a little presentation for calculating g forces of deceleration for a mine hoist conveyance course I'm teaching. Found some great stuff on wikipedia you might want to go over. 1g acceleration results in 32ft per sec/ per sec btw, and that translates into distance traveled of 32 feet per second squared.

- #20

Bob S

- 4,662

- 6

P = (d/dt)·(½·m·v

Bob S

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