# Thread: communication skills I don't have

1. ## communication skills I don't have

I need to discuss the validity of the following statments with two creative examples, I can't seem to put my ideas into words. Any ideas?

a) If the acceleration of an object is positive, it is speeding up. I the accelaeration of an object is negative, it is slowing down.

b)If the velocity of an object is positive, it is moving away from the origin. If the velocity of an object is negative, it is moving towards the origin.

2. Originally Posted by math619
I need to discuss the validity of the following statments with two creative examples, I can't seem to put my ideas into words. Any ideas?

a) If the acceleration of an object is positive, it is speeding up. I the accelaeration of an object is negative, it is slowing down.

b)If the velocity of an object is positive, it is moving away from the origin. If the velocity of an object is negative, it is moving towards the origin.
Note: Both of these depend on what direction you've chosen as positive. For example, most people would choose a postive upward direction for most cases, meaning that a rock freely falling from rest would have negative acceleration and velocity, but it would be "speeding up."

The general rule for a) is this: If the object has a component of velocity in the direction of the acceleration it is speeding up. If the object has a component of the velocity in the direction opposite to the direction of the acceleration it is slowing down. If the acceleration and velocity are at right angles, the speed is constant (at least at that moment.)

-Dan

3. Originally Posted by math619
I need to discuss the validity of the following statments with two creative examples, I can't seem to put my ideas into words. Any ideas?

a) If the acceleration of an object is positive, it is speeding up. I the accelaeration of an object is negative, it is slowing down.
Speed and velocity are not the same thing, speed is the absolute
value of the velocity.

If the object has a negative velocity (in 1 dimension) a positive acceleration
would mean it was slowing down, as it is in the opposite direction to its
velocity. If the object has a positive velocity and a negative acceleration
it is also slowing.

Acceleration of opposite sense to velocity is slowing, acceleration in the
same sense as velocity is speeding up.

b)If the velocity of an object is positive, it is moving away from the origin. If the velocity of an object is negative, it is moving towards the origin.
Not even in 1-D. assume the positive direction is to the right of the origin.
Then positive velocity means the object is moving right (whatever its
position), negative velocity and its moving to the left.

In higher dimensions none of these make any sense.

RonL