Doubts on the sign of acceleration

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In summary, the conversation discusses how to determine the correct sign for acceleration in two different equations. In one case, the acceleration is assumed to be negative, but the answer comes out positive, indicating that the assumption was correct. In the other case, the acceleration is assumed to be positive, but the answer comes out negative, showing that the assumption was incorrect. Ultimately, the minus sign plays a crucial role in determining the direction of acceleration.
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Homework Statement
Let' suppose that a problem says "a car has a velocity of ##5 m/s## and an acceleration such that it stops some seconds later". And I want to solve for the acceleration so I can replace it in another equation.
Relevant Equations
##V_f =v_0 +a.t##
What should I do? Because I have two possibilities. I have ##0=5+at## so ##-5/t =a##. But then I can also say that the acceleration is a negative because it is stopping, so I can write it like ##0=5-kt## and then ##5/t =k##

In case 1 you get a neg value for a which means it was not positive per your assumption in the equation, but rather it is a negative. In case 2 you assumed a was neg and when your ans came out positive, it means you assumed the correct sign for a. Bottom line is when your answer comes out negative, you assumed the wrong sign (direction) ; when it comes out positive, you assumed the right sign.
Ahhhh...the wonders of the minus sign...

1. What is the sign of acceleration?

The sign of acceleration is either positive or negative, depending on the direction of motion. A positive sign indicates that the object is accelerating in the same direction as its velocity, while a negative sign indicates acceleration in the opposite direction.

2. How is acceleration represented in equations?

Acceleration is typically represented by the variable "a" in equations. It is measured in units of distance over time squared, such as meters per second squared or kilometers per hour squared.

3. Can acceleration be zero?

Yes, acceleration can be zero. This means that there is no change in the velocity of an object, either because it is at rest or because it is moving at a constant speed in a straight line.

4. What is the difference between positive and negative acceleration?

Positive acceleration means that the velocity of an object is increasing, while negative acceleration means that the velocity is decreasing. Positive acceleration is often referred to as "speeding up" and negative acceleration as "slowing down."

5. How is acceleration measured?

Acceleration is measured using a device called an accelerometer, which can be found in smartphones, cars, and other devices. It measures the change in velocity of an object over a specific time period and provides a numerical value for acceleration.

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