# Acceleration problem

1. Sep 23, 2007

### starks.L

Is there situations when an object is accelerating but its velicoty is zero ?

2. Sep 23, 2007

### tabchouri

No, you can't have an accelerating object (acceleration <>0) with constant velocity = 0.

Now, you can have an acceleration with velocity =0 only on discrete instants:
when you throw and object upward, it will go up until it stops (velocity=0) for a tiny instant, then falls back. The acceleration of the object is not null and constant = gravity.

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Correct me if I am wrong.

3. Sep 24, 2007

### Meir Achuz

Yes. for example, if you throw an object straight up, it has a constant downward acceleration, but its velocity at the top of its path is zero.
Of course, if there is acceleration, the velocity is not conatant, but is instantaneously zero.

4. Sep 24, 2007

### Loren Booda

If acceleration is zero (no change in velocity), and velocity is zero at one point, velocity is always zero.

If acceleration is zero (no change in velocity), and velocity is nonzero at one point, velocity is always that nonzero value.

If acceleration is a nonzero constant, the velocity is at sometime instantaneously zero.

A changing acceleration does not necessarily imply any particular velocity.

5. Sep 24, 2007

### Mk

No. If constant velocity (implied constant direction), no change in acceleration.

That's the standard textbook answer, but Meir Achuz's sounds right to me:

Last edited: Sep 24, 2007