# Speed vs Acceleration: What's the Difference?

• MoMo
In summary, speed is a scalar quantity that measures how fast an object is moving, while acceleration is a vector quantity that measures the rate of change of velocity. Velocity, also a vector quantity, refers to the speed and direction of an object's movement. When a car accelerates, its speed increases as long as acceleration and velocity are in the same direction. Velocity is important in understanding the relationship between speed and acceleration, as it is the speed and direction of an object's movement.
MoMo
Could someone please explain what the difference is between speed and acceleration? I would sincerely appreciate it, thanks!

What are their definitions?

speed - a scalar quantity, which refers to how fast an object is moving

acceleration - a vector quantity, which is defined as the rate of change of velocity

...erm let me add velocity's def here as well:

velocity - a vector quantity, which refers to the rate at which an object changes its position and is computed from the displacement/time ratio

See, what confuses me is when I compare speed and acceleration in terms of a car. When a car accelerates, doesn't its speed increase? What does velocity have to do with these two terms as well? Btw thanks again :-)

MoMo said:
See, what confuses me is when I compare speed and acceleration in terms of a car. When a car accelerates, doesn't its speed increase?
Acceleration is the rate of change of the velocity. So as long as acceleration and velocity are in the same direction, acceleration will result in increased velocity.

Don't forget that when you hit the brakes, the car also accelerates--just in the opposite direction to the velocity vector (or at least you hope it does).

MoMo said:
What does velocity have to do with these two terms as well?
Velocity is the speed of the car and its direction.

Last edited:
That makes sense. Thank you :-)

MoMo said:
That makes sense. Thank you :-)
My pleasure.

## What is the difference between speed and acceleration?

Speed and acceleration are both measurements of an object's motion, but they measure different aspects of it. Speed is the rate at which an object is moving, while acceleration is the rate at which an object's speed is changing.

## How are speed and acceleration related?

Speed and acceleration are related in that acceleration affects an object's speed. If an object is accelerating, its speed will either increase or decrease depending on the direction of the acceleration. If an object is not accelerating, its speed will remain constant.

## Can an object have a high speed but low acceleration or vice versa?

Yes, an object can have a high speed but low acceleration. For example, a car traveling at a constant speed on a highway has a high speed but zero acceleration. On the other hand, an object can have a low speed but high acceleration, such as a ball being thrown straight up in the air.

## How is acceleration measured?

Acceleration is measured in units of distance over time squared, such as meters per second squared (m/s²) or feet per second squared (ft/s²). It can also be measured using an accelerometer, which is a device that measures changes in velocity.

## Can an object have a negative acceleration?

Yes, an object can have a negative acceleration. This means that the object's speed is decreasing. Negative acceleration can also be referred to as deceleration or slowing down. For example, a car braking to come to a stop has a negative acceleration.

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