Is velocity zero when direction changes?

[00945584]

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The moment an object changes direction is velocity 0 or does it exist.

For example if I go 5 m/s to the right and then all of a sudden go 10 m/s to the left. Is it at that moment I change direction velocity becomes zero.

Also, so if an object is constantly changing direction then velocity is there or not there. In this case what is velocity, the value?

I mean the value in terms of linear velocity.
I think angular velocity is constant.

 

[00945584]

anyone i would appeciate it

 

[Fort]

At that moment, yes, the velocity is zero. Picture a smooth curve with velocity plotted versus time. When the velocity curve crosses the time axis, the object's instantaneous velocity is zero.

For your second question, remember that velocity is a vector. So if that vector is constantly changing direction, the value of the velocity at any moment will only depend on that vector's magnitude.

 

[00945584]

but for the second question velocity is both mag. and direction. how can magnitude only be taken into account when velocity is constanting changing direction. therefore i am wondering if velocity is 0 or what a number.

 

[Fort]

but for the second question velocity is both mag. and direction. how can magnitude only be taken into account when velocity is constanting changing direction. therefore i am wondering if velocity is 0 or what a number.

The value of the velocity, or the magnitude, is only dependent on its components at that moment. Just because the velocity, that is the vector, is changing does not mean the value of it is changing.

Imagine yourself twirling a ball at the end of a string. The velocity, that is, the vector, is changing because it's constantly changing direction, but the magnitude is not. So the value of the velocity won't necessarily change just because the vector itself is changing.

 

[loveoforganic]

It sounds like you're talking about an unrealistic situation in which you can instantly change velocity from 5 m/s to the right to 10 m/s to the left. In that instance, you would have no moment of 0 velocity - you would just have a discontinuous graph if you were to graph the velocity, and if you were to graph the acceleration, you'd get a vertical line that went to infinity. In realistic situations though, changing from 5 m/s to the right to 10 m/s to the left, assuming you're moving along a straight line, requires that there is a moment of 0 velocity.

 

[sv3]

perhaps the above posts were only regarding magnitude but if you do somehow magically do as described in your first scenario, when the velocity has a magnitude of zero, there is still an acceleration there, hence the fact that after you have zero velocity, you then have non-zero velocity. I think the slope on a v vs t graph would be negative (Assuming your intital direction was in the positive direction) indicating there is an acceleration. A flat slope would mean no acceleration and a vertical slope would mean acceleration is present (after doing a couple of hundred practice problems, i have never come across the vertical slope scenario though......)

 

[loveoforganic]

Just plug in the numbers, for the impossible theoretical.

a = (vf - vi) / (tf - ti). If it occurs in 0 seconds, tf = ti, and you end up with a value over 0. Whether your graph of acceleration is infinite in the positive or negative directions depends on the coventions you assign your velocities.

 

[sv3]

your totally correct. When I read the original question, I still envisioned the velocity having to go through the entire range (I pictured a very very steep graph in my head) and thats where my answer came from. You can't do it in zero time. not possible