Apparently you can. This is why we started with distance v. displacement and moved on to speed v. velocity. Acceleration is defined as the

__rate of change of velocity__(not speed).__Linear Acceleration__

Linear acceleration occurs as the athlete increases speed running down the vault runway (

*figure*7).Between positions #1 and #2, the athlete increases his velocity (speed toward the vault table) from 0

*ft/s*to 4*ft/s*. At each position, he has again increased his velocity, reaching 12*ft/s*before he reaches the vaulting board.*acceleration = change in velocity / time*

*a =*

*D*

*v /*

*D*

*t*

This explains accelerating by increasing speed. You can however, accelerate without increasing your speed.

__Constant Acceleration__

Figure 8 |

*ft/s*and still accelerate.

__Whenever an athlete changes direction, he is accelerating__(

*figure*8).

Note the change in arrow direction for each position. His change in displacement is not in a straight direction, but angular. Thus his displacement, as a vector, is constantly changing.

Even though this athlete hasn’t changed his speed, he is constantly changing his direction, thus accelerating. This is known as Constant Acceleration.

*acceleration = change in velocity / time*

*a =*

*D*

*v /*

*D*

*t*These are the same equation. They have a different result because

**is a vector.***v*__Changing Acceleration__

But what happens if the athlete does increase his speed while running in circle? This is called Angular Acceleration (

Figure 9 |

*figure*9).This discussion is not yet ripe, so we’ll come back to angular acceleration later when we discuss rotation.