dojj

iTrader: (3)

so why does it still keep going up when you throw/hit it away?

it can't just be the deflection caused by it's shape distorting can it?

alistairolsen

BIG difference between continuing to go uo, and accelerating!

It goes up, but more and more slowly till eventually it peakes and begins to come down, but it is decellerating from when it leaves your hand.

alistairolsen

contradict myself? Care to point out where?

to continue to accelerate it would require a force, if this happened it would also result in it moving faster just after it left your hand, then when it left your hand which is NOT the case.

if it leaves your hand at 9.8m/s, and gravity imposes an acceleration of -9.8m/s^2 then it will continue upwards for one second, until its velocity is zero, at which point it will continue accelerating at the same rate, but will now be travelling in a different direction!

so saying that it continues upwards is of NO consequence to whether it is still accelerating or not!

les3002

it keeps going up as it takes time for the inertia force and gravity to decelerate the ball back to 0 and then accelerate it back towards the ground.

alistairolsen

well read the thread before you act like a cunt then mate

Red16

Bingo!

PhilM

Jesus....all this crap on this thread

Your acceleration will of course start to decrease when you lift off.

Ie, the ball leaves your hand doing 20m/s, it will immediately when released decelerate at about 10m/s, so after ~ 2 seconds its velocity will be zero.

Ask a school kid for their science book and be amazed

Mr Whippy

Some people need to start to realise the difference between "the rate of change of speed" (IE acceleration/Deceleration) and speed its self.......

tabetha

I can't beleive anyone believes the accelration could continue without ENERGY being imparted by the car's engine.
The instant you either lift foot off gas or dip clutch, you start to deccelerate, might be a slight amount but it cannot be any other way, otherwise you could merely accelrate to speed dip the clutch and keep going at 60 mph for hundreds of miles, you could in space as there is little gravity and no atmosphere.
Basic theory, "for every action there is an equal and opposite reaction".
A car has NO potential energy only energy which you provide with the engine by burning fuel.
Any ball thrown in the air will start to deccelerate immediately unless another force is applied, ie if you throw it downwards gravity would be a factor, the same factor that slows a car, as well as wind resistance etc.
tabetha

rsnissan

iTrader: (9)

some people should have paid more attention at school

gingeRS

the crap written on this thread is priceless

people should have paid more attention in school i feel

foreigneRS

i find it incredibly ironic that on the same page there is another post by dojj complaining of someone else's stupidity

Iain Mac

Well my head hurts - too much science for one day....

AlexF

HAHA classic!

take that chip

Turby2

You only need to look at some vehicle data logging to see loss of speed, although small, during a gear shift. The faster the shift the less speed that is lost. ie less time spent with torque disconnected between engine and wheels.

That's also one of the reasons why competition cars use dog-boxes and sequential boxes to reduce the shift time.

I'll try and dig out some of my motec data logging if I remember which clearly shows it happening.

foreigneRS

Turby2 why bother? if these people can't understand basic physics, do you think that they can interpret a datalog?

dojj

iTrader: (3)

i'll hold my hands up to being a bit slow on the uptake for this sort of stuff, but, once it's all been explained it makes perfect sense

i'm more concerend that several of you seem to be providing confliciting arguments for one or the other of the answers given

and then there is the tennis ball theory and the 100 mph theory, none of which were actually relevant to the question i was asking, but intresting enough anyway

Rod-Tarry

Its almost 50 years since my O level science in those days cars didnt acclerate, just sort of plodded along.
Although Chips teacher response is rather aggressive he is correct.

GARETH T

i think some people have discovered the perpetual motion machine

AlexF

I think you lot are making it all up though...

you all think acceleration is a stright line thing... its not

Then theres inertia....

ECOS95

Thats a very good way to look at it.

nilrem

so sorry i was arguing the accelertion was still continuing after the clutch was dipped... i was a twat (and very drunk for that matter!) f=ma and all that...

tabetha

And the perpetual motion machine ran for twelve years!!
tabetha

Chip

iTrader: (3)

Take what?

Of course if your car has just dropped off a cliff or is on a massive decent its going to accelerate unless its at terminal velocity, but what the fuck has that got to do with the question or my answers?

Likewise if you happen to be doing 30 when you let off the clutch to change into second and at exactly that moment you get hit by an artic doing 50mph your car will accelerate, thats totally irrelevant too though of course.

geoffxr4

Interesting idea and i have absolutely no idea. But basically it comes down to would a graph of acceleration vs time come back to the zero point over a split second, therefore still experiencing acceleration although less than the original, or would the drop from a certain acceleration to zero acceleration be instantaneous the moment the forward force is removed.

I think a graph from NASA show's quite clearly what would happen when the forward thrust is removed!

http://history.nasa.gov/ap08fj/pics/tli-g.gif

Interesting discussion though, get's you thinking

but chip was right

Fast Guy

Here's a printout of one of my 0-60runs done at York raceway.
To me it looks like acceleration tails off very rapidly then holds speed before I hit the next gear. I assume it just doesn't have enough time to noticeably decelerate in the 1/4s or so this takes to happen.

foreigneRS

don't let datalogs like that above confuse you - it is not possible to increase speed in between gearchanges (unless free falling down a fucking steep hill). it's just because the datalogger is too slow that it looks like it is