Define: acceleration?

Question

According to my physics revision book, the definition of accelertion is 'the change in velocity per second'. But the last time i checked, it meant the change in speed per second...
For example, if a car's speed is gradually increasing, you'd say it is accelerating.
However, if a car is travelling at a constant velocity of, say, 2m/s NORTH, and then changed its velocity to 2m/s WEST, still mantaining a constant speed, you would not say it is accelerating, you'd simply say it has changed its velocity
So why is acceleration seen as the change in velocity rather than the change in speed?
The whole subject really confuses me, so i'd really appreciate helpful, explanitive answers
Thanks :)

Answer 1

In Physics acceleration is a measure in the rate of change in velocity in relation to time, for example the time it would take for a stationery car to reach say 40 mph. However velocity is a vector (ie direction) and therefore any change in its vector is also a change in its acceleration.

Answer 2

Define Acceleration In Physics

Answer 3

Acceleration is defined as the rate of change of velocity with respect to time. If a body were to slow down, speed up, or CHANGE DIRECTIONS., then it is called acceleration. This is the definition. I do not think there is a way in which a body can change direction without changing velocity, so that means acceleration must be a vector quantity in order to describe the motion of an object.

Answer 4

In physics, velocity is speed in a given direction. Speed describes only how fast an object is moving, whereas velocity gives both the speed and direction of the object's motion. To have a constant velocity, an object must have a constant speed and motion in a constant direction. Constant direction typically constrains the object to motion in a straight path. A car moving at a constant 20 kilometers per hour in a circular path does not have a constant velocity. The rate of change in velocity is acceleration. Velocity is a vector physical quantity; both magnitude and direction are required to define it. The scalar absolute value (magnitude) of velocity is speed, a quantity that is measured in metres per second (m/s or ms−1) when using the SI (metric) system. For example, "5 metres per second" is a scalar and not a vector, whereas "5 metres per second east" is a vector. The average velocity v of an object moving through a displacement (Δd) during a time interval (Δt) is described by the formula:

v =∆d/∆t

The rate of change of velocity (in m/s) as a function of time (in s) is acceleration (in m/s²) – how an object's speed or direction of travel changes over time, and how it is changing at a particular point in time.



Acceleration is the rate of change of velocity with time. In one dimension, acceleration is the rate at which something speeds up or slows down. However, since velocity is a vector, acceleration describes the rate of change of both the magnitude and the direction of velocity

Answer 5

In physics, speed and velocity are different things. Velocity also has a direction of motion. Acceleration is a change in velocity - hence turning a corner at a constant speed is also acceleration because your direction and therefore your velocity are changing.

Answer 6

Yeah it's weird but I think acceleration is actually 'the rate of change of velocity in time', in physics it gets real specific when you have to distinguish between distance and displacement. Velocity is rate of change in displacement. With acceleration if you change direction because velocity takes into account direction( as it is a vector) you have changed velocity and therefore you've accelerated.