Position,Velocity,Acceleration!!

I have a problem here.Suppose a particle starts from the origin , x=0, with no velovity but with a positive acceleration.Under this acceleration the particle gains a positive velocity and moves in a positive direction.Can anyone explain this physically.
I am not able to physically imagine a particle with zero velocity(rate of change of displacement) and positive accleration(rate of change of velocity)

 

[Hush]

Hold a brick above the floor then release it. At the instant you let go it has zero velocity but is now accelerating at 32 ft/s^2.

 

Hush, thanks for the reply.Suppose i hold the brick in my hand let the hand be the origin at t=0, x=0; now i release it at say t=2 secs. x =2cm. say,
so velocity=ds/dt=(2-0)/(2-0)=1cm./sec.
This is at the end of 2 secs.Can u explain like this with regard to acceleration?Please

 

[Hush]

You should have learned this stuff in secondary school. If you're still in school you should ask your math teacher for a refresher. At any rate I'll see what I can do for you.

If acceleration is constant,

Acceleration at time t A(t) = Ao
Velocity at time t V(t) = Ao *t + Vo
Position at time t X(t) = (Ao*t^2)/2 + Vo*t + Xo

For your example:

Initial acceleration Ao = gravity = 9.81 m/s^2, initial velocity Vo = 0, & initial position Xo = 0

V(2) = 9.81*2 + 0 = 19.62 m/s & X(2) = (9.81*2^2)/2 + 0*2 + 0 = 19.62 m
V(3) = 9.81*3 + 0 = 29.43 m/s & X(3) = (9.81*3^2)/2 + 0*3 + 0 = 44.15 m
V(4) = 9.81*4 + 0 = 39.24 m/s & X(4) = (9.81*4^2)/2 + 0*4 + 0 = 78.48 m

And so on.

 

[quark]

Hush!

Though I couldn't understand the purpose of this question, I really liked your spirit. (of not bothering about academic vs professional) This attitude does keep this site lively.

Cheers,

Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.

 

[electricpete]

It sounds to me like gendoubt is trying to reconcile the math with his intuition. That is always a useful excercize for all of us.

 

You are right electricpete!!Though i may sound immature, i always like to know how others think of a physical phenomenon(however simple it may be).It helps me to think better and move a step forward with my thoughts.
You could put in your thoughts too(in a physical sense) to the question.Thanks very much cause i started feeling a bit down before your comment.

 

[Hush]

My apologies gendoubt,

As my Grandad said:

There's no such thing as a stupid question, just stupid answers.

 

[dkf]

To Hush
Just about questions:
Your Grandad was a wise person!
I was always feeling uneasy to pose questions till the other day when I saw: Bad question is the one that was not asked.

 

[olindude]

If you throw a ball straight up in the air, it eventually stops and then comes back down. At the top of its trajectory, it has zero vertical velocity, but it has constant acceleration (from gravity).

 

[mhoons]

A further perspective: Everything on earth is under the influence of the acceleration of gravity at approx 32 ft/sec^2. Even the brick sitting on your floor is experiencing this acceleration. That's what keeps it on the floor. It's just not moving. That's why it has weight when placed on a scale. If the floor is removed from underneath the brick, the brick will then begin to move and the velocity will steadily increase because of the gravitational acceleration that it has always been there.

 

[ivymike]

Does that mean that acceleration is not the time-derivative of velocity? Are you saying that an object can accelerate indefinitely without ever experiencing a change in velocity? Or are you saying that the object is experiencing an "acceleration" due to gravity in one direction, and an "acceleration" due to the floor in the opposite direction, with a net acceleration of 0?

 

[stuff]

A set of statements to contemplate:

The force due to gravity has the effect of acceleration on a mass when there is no opposing force on that mass.

A mass in a gravitational field results in a force. This is a concept that man has still not conquered!

It requires force (or net force to be correct) to accelerate a mass.

I always find it entertaining to consider the action of the earth when a mass is released. Every force has an equal and opposite reaction.....when you release a mass and let it fall by gravity, the earth has to move towards it to balance the forces (an immeasurably small amount, mind).

 

[meintsi]

mhoons -

Think about what you just said.
Then go back to Physic 101..........


Remember...
"If you don't use your head, your going to have to use your feet."