# Physics

## 15 terms · My ninth grade physics vocabulary.

### Mechanics

The study of the motion of objects.

### Kinematics

The describing of the motion of objects using words, diagrams, graphs, numbers, and equations.

### Scalar

A quantity that is described by a numerical value alone.

### Vector

A quantity that is fully described by both a numerical value and a direction.

### Distance

A scalar quantity that refers to how much ground an object has covered during its motion.

### Displacement

A vector quantity that refers to how far out of place an object is; the object's overall change in position.

### Speed

A scalar quantity that refers to how fast an object is moving.

### Velocity

A vector quantity that refers to the rate at which an object changes position.

### How to get average speed

Distance traveled divided by the time of travel.

### How to get average velocity

Position divided by time equals displacement divided by time.

### Instantaneous speed

The speed at any given instant in time.

### Average speed

The average of all instantaneous speeds, found simply by a distance over time ratio.

### Acceleration

A vector quantity that refers to the rate at which an object changes its velocity. As long as the object's velocity is changing, the object is accelerating.

### Constant acceleration

When the velocity of an object is changing at a constant speed.

### How to get acceleration

Acceleration equals velocity divided by time.