Can an object have negative acceleration and negative velocity?

Question

I'd like an example of this please.

Answer 1

Okay, here's the deal: stick with me and meg because otherwise you're going astray.

BOTH velocity AND acceleration can be positive or negative depending on the case. rocket car (thrusters on the front and the back) driving past us from left to right as we watch. The car is moving at a constant velocity of +X meters per second. (we just defined "to the right" as being the positive direction of motion). The acceleration here is 0

The car then fires it's front thrusters... slowing it down. It has a negative acceleration at this point (because the change in velocity per the change of time is a negative number since to the right is positive) but it still has a positive velocity.

The car comes to a stop and begins to move in the opposite direction (to the left). The car now has a negative velocity since it is moving away from what we have defined as positive. As the thruster continues to fire, the car gains speed... Here's the important part: the acceleration is STILL negative even though it's gaining velocity. (for clarity: negative acceleration does NOT mean the same thing as deceleration or slowing down)

Now the front thruster shuts off and the rear thruster kicks back on, again slowing the car down. The car is still moving to the left (negative velocity) but it is accelerating in the positive direction (toward the right... positve acceleration).

The car again comes to a stop and reverses direction, gaining speed as it moves back to the right. Since we defined "to the right" as positive the car now has positive velocity AND positive acceleration.

Let's recap:
Velocity and acceleration are positive or negative depending on direction and how you have defined your frame of reference.
Acceleration is negative if it is in the opposite direction of your positive direction on your frame of reference. This is REGARDLESS of whether you are speeding up or slowing down.

Answer 2

Both velocity and acceleration are vector quantities, that is they have a magnitude, which is always positive, and a direction. Once you define a positive direction, for example moving to your right, then there is a negative direction, to your left. People will say -v when what the mean is v going in the negative direction, or a rocket has an acceleration up (a) due to its engines, but experiences a acceleration of - g (down) due to gravity. The net force on the rocket is F=m(a-g)

Answer 3

THE FIRST FEW ANSWERS ARE WRONG

This is possible.....The following is an example with relation to height:
An object is dropped from a plane in the sky. The object has a negative velocity (because it is traveling down from the plane). Gravity has a negative acceleration on freely falling objects so the object is falling at a negative acceleration of 9.8 m/s/s. Negative velocity and acceleration.

Answer 4

Yes, an object can have both a negative acceleration and a negative velocity. A velocity is a speed in one direction, as oppossed to a speed which is just a speed in any direction, and which can change direction at will. So let's say you have a car going at 30 mph, if the car stops and then reverses in the exact opposite direction, it will have a negative velocity, because it's going in an opposite direction to the original velocity (which was forward). A negative acceleration is when an object is slowing down. So let's say we have a car travelling at 30 mph constantly, in a forwards direction. This car has a positive velocity (if we take forwards to be positive), and because it is travelling at a constant speed it has no acceleration, because it isn't getting quicker or going slower. If the car speeds up it will have a positive acceleration because it is speeding up, however if the car slows down it will have a negative acceleration because it is slowing down.
Hope this helps.

Answer 5

Negative acceleration is possible, acceleration is a scalar value, negative acceleration simply means you are slowing down. A classic example is the acceleration due to gravity when calculating ballistic motion is considered a negative acceleration, because it always opposes the force applied to the projectile in the y-axis.

Velocity is a vector measure and by definition can not be negative. Vectors have a direction and amplitude, because the direction is defined by the vector, the amplitude of the vector is never be negative. Mathematical operations on a vector result in a new vector with a different direction and amplitude, but the amplitude is again always positive.

I saw a couple of people use the term speed interchangeably with velocity, but speed is not the same it is the scalar average value of velocity and therefore not a vector.

Answer 6

An object can have a negative acceleration but it can not have a negative velosity. An object can have a negative acceleration when it is deselerating. For example when an object moves from 30m/s of velosity to 10m/s it will have a negative acceleration.

Answer 7

In theory, yes. That is what we call time travel. There have been publications citing high energy particles defying (travelling beyond) the speed of light, which would imply "time travel" or "negative acceleration." Also, it will be important to note that the idea of negative acceleration is relative to time moving forward. Another place to look for negative accelleration is on either side of an event horizon. Hope this helps.

Answer 8

negative acceleration n negatice velocity means if u go agains the direction of motion

u do hv negative acceleration wen u apply brakes on a moving vehicle

so negative acceleration does exist
n if u determine ur direction of motion suppose straight
n u r in the reverse gear tht is a negative velocity

Answer 9

no, velocity is positive whether your going backwards or forwards. direction doesn't matter, your still going backwards in a positive velocity/acceleration. put your car in reverse and drive.....your going backwards at a certain MPH. examples are cars, planes, trucks, balls, sex, sound frequencies.....you name it.

Answer 10

It is a matter of vectors.