(usually written m/h).

Speed is the

rate

at which something moves.

The

speed

of an object is the distance it travels over a certain amount of time.

Speed

The speed of the Milky Way galaxy is about 600 km/s.

Examples of speed:

How do you calculate speed?

Speed =

distancetime

For example, a cyclist travels 30 kilometers in 2 hours, and so her speed is 15 km/hr.

Speed =

30 km

2 hr

=

15 km/hr

How do you calculate speed?

Speed =

distance

time

**Speed and**

**Velocity**

Set world landspeed record in 1997: 763 mph.

Thrust SSC:

Instantaneous speed

is the rate at which an object is moving at a given instant in time.

Example: Car speedometer (60 mph right now)

How do you calculate speed?

Speed =

distance

time

Total distance (d) = 100 km + 50 km = 150 km

Total time (t) = 1 hr + .5 hr = 1.5 hr

Average speed (v) = =

100 km/hr

**Speed**

describes only how fast an object is moving

.

describes only how fast an object is moving

.

**Velocity**

gives both the speed

and

direction of the object's motion

.

gives both the speed

and

direction of the object's motion

.

**60 km/hr**

**60 km/hr North**

**What's the difference?!?**

150 km

1.5 hr

2 Types of Speed

1.

2.

average speed =

total time

total distance

Average Speed

is the total distance traveled (d) divided by the total time (t).

Example: You drive 100 kilometers over an hour, then pull over to eat. When finished eating, you drive another 50 kilometers which takes you half an hour.

http://video.nationalgeographic.com/video/the-magazine/the-magazine-latest/ngm-cheetah-speed-record/

Calculate the speed with which a sprinter runs, in meters per second, if she can cover 100 meters in 10 seconds.

Speed of sprinter = 100/10 = 10 m/s

A lion chasing a gazelle across the plains of Africa covers a distance of 400 feet in 30 seconds. If the gazelle is running at a speed of 13.5 ft/s will the lion be able to catch it?

Speed of lion = 400/30 = 13.3 ft/s

The gazelle is too fast!

Practice!

1 tire rotation = 3 ft

The time is takes for 1 rotation = .034 second

3/.034 = 88 ft/s

88 ft/s = 60 mph

Practice

time = distance / speed

distance = speed x time

How to calculate time and distance

What if the time for 1 rotation = 1 second?

3/1 = 3 ft/s

3 ft/s = 2 mph

You run 4 kilometers over an hour, then you stop for a break. You continue your run for another 6 kilometers which takes you an hour and a half. What was your average speed?

total distance = 4 km + 6 km =

10 km

total time = 1 hour +

1.5 hours

average speed =

10 km

/ 2

.5 hours

= 4

km/hr

How long does it take Cory to walk to school if he lives 2,000 meters away and his speed is 2 m/s?

time = 2,000 / 2 =

1,000 s

How far away from school does Joe live if it took him .5 hours to walk to school at 5 mi/h?

.5 x 5 =

2.5 miles

Speed or Velocity?

42.3 m/s

16 km/sec downhill

17 km/min South

12.5 km/hr

23.9 m/s

17.31 Northeast