At what point is displacement (in physics) negative? What does this mean?

Answer 1

Displacement is a vector, which is never negative. It has a positive magnitude and a direction. After you define a coordinate system, a displacement vector may have a negative component.

Answer 2

Displacement is a vector. It has magnitude and direction. The direction is dependent on the direction of the object’s initial velocity. In the example below, a ball is thrown upward. This is the positive direction. Since it accelerating toward the street, the acceleration is negative.

Displacement = final position – initial position

One of the most common examples is when an object is on top of building. For example, the building is 30 meters tall. A ball is thrown upward at 20 m/s. Let’s use the following equation to determine the ball’s velocity just before it hits the street.

vf^2 = vi^2 + 2 * a * d. a = -9.8 m/s^2, d - -30 meters
vf^2 = 20^2 + 2 * -9.8 * -30
vf = ± √988

This is approximately 31.4 m/s. Since the ball is moving downward, its velocity is negative. Let’s use the following equation to determine the time.

vf -= vi + a * t, a - -9.8 m/s^2
-√988 = 20 – 9.8 * t
t = (-√988 + -20) ÷ 9.8

This is approximately 5.25 seconds. I hope this is helpful for you.

Answer 3

It's made to confuse people. And time and time again, it does. So they ask here.
The problem is, it is a CONVENTION, not a rule, and can often depend on what or where you are taught.
It simply means a movement distance opposite to a movement distance that is DEEMED to be in a positive direction. By who?
There is nothing definite about it. I hate conventions.

Answer 4

Displacement is the length or distance from an absolute position for starting point to an absolute position for end point. Making the origin at the starting point and the first displacement along the z-axis, we get positive displacement to any end point to the right side of the origin and negative displacement to any end point on the left side of the origin.
This is displacement along the z-axis.

Answer 5

Positive is the opposite of negative.
So negative displacement means that you have moved in the opposite direction to whatever YOU have called positive.
It means nothing else.

If you use 2 or 3 dimensions then positive and negative, on their own, become meaningless and we need to use an angle or two or we need to use components.

Once more the phantom thumbs downer. If they had anything real to add they would add it in a comment. Surely?

Answer 6

It depends what sign-convention is being used.

For simple problems where we are only interested in movement in 1 dimension:

If we are dealing with horizontal motion, then we *usually* take right as positive and left as negative (like +x and -x axes on a graph). Moving 3m right is a displacement of 3m. Then moving 7m left is a displacement of -7m. Total displacement = 3m – 7m = -4m. That means we end up 4m left of where we started.

If we are dealing with vertical motion, then we *usually* take up as positive and down as negative (like +y and -y axes on a graph). Moving 5m down is a displacement of -5m. Then moving 6m up is a displacement of 6m. Total displacement = -5m + 6m = 1m. That means we end up 1m above where we started.