physics question

MB44

Please try answer this!!!!!!
Give an example of a body with zero velocity and not zero acceleration
2. give an example of a body with zero acceleration but not zero velocity.

casso

I think something standing on a merry go round or something like that has 0 vel but has accel.

Something moving at a regular speed (ie not getting faster or slower) has 0 acceleration but has velocity.

Not too sure about the 1st on, sorry.

MB44

thanks anyways

Abdiel

MB44 wrote:

Give an example of a body with zero velocity and not zero acceleration

when a ball is thrown up into the air, at the point where it stops going up and starts to come down it has an instantaneous velocity of zero but would still have an acceleration of 9.8 m/s*s

MB44

that was perfect now just one of the opposite

Abdiel

casso was correct on that one - something moving at constant velocity has zero acceleration

Poz3D

Could you have a car accelerating into a brick wall as an example for the first one? (Or is that just force without a resultant velocity?)

The answer to the second one would be a car travelling at a constant speed (such as 50mph). If it's constant, then there's no acceleration, but there will be velocity as it is moving over a distance.

Hope this helps

MB44

thatnks . was a great help

Capt'n Midnight

MB44 wrote:

Please try answer this!!!!!!
Give an example of a body with zero velocity and not zero acceleration
2. give an example of a body with zero acceleration but not zero velocity.

zero velocity is kinda difficult since everything is relative and the universe is expanding etc.
zero velocity relative to another body is easy though.

bcKay

Could you have a car accelerating into a brick wall as an example for the first one? (Or is that just force without a resultant velocity?)

You'd still have velocity in this case. Maybe not for the front end of the car...but for the back end...lol...it's all relative
The ball is the best example...but if you define a starting point and an end point on a circle to be the same spot...a car travelling will have no change in velocity but will have accelerated. :S hope that helps.

planck2

A body carrying out simple harmonic motion is the answer to both questions.It has maximum velocity when it has zero acceleration and maximum acceleration when it has zero velocity.

planck2

Capt'n Midnight wrote:

zero velocity is kinda difficult since everything is relative and the universe is expanding etc.
zero velocity relative to another body is easy though.

Nonsense. The fact that the universe is expanding has really nothing to do with the answer to this question at all.The expansion of the universe as predicted by Einstein is accounted for by the vacuum energy of the space- time and relates to a different set of physical ideas.

If I am asking the question and i am standing still then answers relative to me are important. To someone accelerating and observing a simple harmonic oscillator, the motion of the oscillator will look more or less the same to the guy standing still, there will be some change of phase to the motion, but still zero acc with max veloctiy, all one has to do is use the momentarily co moving co-ordinate frame.

planck2

I've one problem with this account of an harmonic oscillator as viewed from an accelerating frame, the one in which the oscillator has zero acceleration

dudara

The second question seems a bit silly, something with non-zero velocity and zero acceleration can be anything moving at a constant speed in a straight line.

To add to this, a body can still have acceleration even at constant speed, when moving in a circular path.

bcKay

body can still have acceleration even at constant speed

This is true, but a constant speed isn't a constant velocity if it's travelling in a circular path.

dudara

That was why I used the words "constant speed" and not "constant velocity"

By it's vector nature, constant velocity means zero acceleration.

bcKay

ah ok...I was confused (no comments--it was 1am local ) since the question was velocity...but I'm back on track now!