# Physical Science - Chapt. 11

## 32 terms

### motion

an object's change in position relative to a reference point

### frame of reference

stationary background needed to detect motion

### vector

a quantity with direction

### displacement

the change in position of an object

### speed

how fast an object moves

1. m/sec
2. km/hr
3. mph

### constant speed

an object moves equal distances in equal times

### instantaneous speed

speed at a certain time (speedometer)

### How does average speed differ from instantaneous speed?

average is speed calculated over a time interval; instantaneous is the speed at a certain time (speedometer)

### velocity

speed in a direction

### acceleration

the rate of change in velocity

### What causes acceleration?

Change in speed or change in direction.

### centripetal acceleration

the acceleration of an object moving in a circle

### What mathematical equations define acceleration?

1. a = vf - fi / t
2. vf= vi + at

### What units are used with acceleration?

m / sec / sec or m / sec2

slowing down

a push or a pull

unit of force

### What are the 4 fundamental forces?

1. gravity
2. electromagnetic
3. strong nuclear
4. weak nuclear

strong nuclear

gravity

### unbalanced forces

forces that don't cancel out

### How do unbalanced forces affect motion?

they cause acceleration

### balanced forces

sets that cancel out

### friction

force between objects that opposes motion

1. static
2. sliding
3. rolling
4. fluid

### static friction

friction between objects at rest

### kinetic friction

friction between moving objects

1. sliding
2. rolling
3. fluid

lubrication