# Motion Problems

1. Sep 9, 2006

### mini_smurf13

1) If the velocity of a particcle is zero, can its acceleration be zero? Explain.

2) Consider the floowing combinations of signs and values for velocity and accleration of a particle with respect to a one-dimensional x axis.

Velocity | Acceleration
1. + | +
2. + | -
3. + | 0
4. - | +
5. - | -
6. - | 0
7. 0 | +
8. 0 | -

Describe what a particle is doing in each case, and give a real-life example for an automobile on an east-west one dimensional axis, with east considered the positive direction.​

I do not understand this at all! Please please please please help if you can with as much as you can. ANY help will be greatly appreciated because I have no idea what to do.

2. Sep 9, 2006

If the velocity of a particle is zero, it's acceleration must be zero. Backwards: if the acceleration of a particle is zero, it's velocity can either be zero or constant.

3. Sep 10, 2006

### E=m(C)^2

Alright for question 2 in the first scenario the particle is travelling east and it's velocity is increasing as acceleration is positive. In the second the particle is once more travelling east but it's velocity is decreasing as acceleration is negative. In the third it is travelling east with constant velocity and fourth travelling west with increasing velocity.
Can you begin to get the idea? Hopefully that helps.

4. Sep 10, 2006

### Delzac

BTW, must acceleration be zero when at that INSTANT the velocity is zero?
i think no, there can be acceleration when velocity is zero, but when the period of Zero Velocity stretchs for more that an "instant". then yes, acceleration must be zero.