<::Speed::>

Speed

:: | Instantaneous Speed | ::


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Speed

Speed is related to time and distance. When you drive a car down a 50 km road in 1 hour we say you are driving at a speed of 50km/h.

Average Speed

Average speed is ythe total distance divided by the total time for a trip.

The equation would look something like this:

The Symbol or Equation	Explaination
V_{av = d/t}	This is the equation for average speed **remember this equation
	This is the symbol for "change in" also known as delta
d	This means the change in distance, "elapsed distance" or "distance"
d = d₂ - d₁	d₁ is where the first measured distance and d_{2 in the second measured distance. d}1 is usually 0
t	This is the "change in time," elapsed time," "period of time,"t or "time."
t = t₂ - t₁	t₁ is the first time measurement and t_{2 is a later time measurement. t}1, the start time, is often zero.

Quantity symbols

These are italic letters used to represent quatities like distance, time and speed in a scientific equation. A letter can be used again to represent another quantity, for example d can mean distance, diameter, or density.

Instantaneous Speed

Instanteous is the speed of an object at a particular instant of time. Intrustments that measure instantaneous speed are speedometers and "radar guns.".

Constant Speed

Constant speed is when instantaneous speed stays uniform for a period of time. Cars and airplanes alike have devices called cruise control to keep a constant speed.

Sample problem 1

The distance from Simran's house to his school was 4.7 km. He walked to his school in .25 hours, wut was his average speed?

Step 1: State the given information.

d =4.7 km
t = .25 Hours
V_av = ?

Step 2: State the equation and modify the equation when needed

V_{av = d/t}

Step 3: Answer the question filling in the given information into equation.

V_{av = 4.7km/.25hours

V}av = 19 km/h (**remember to following the Certainty/Significant Digit Rule)

Step 4: Write the answer in sentence form

Simran's average walking speed to his school was 19 km/h (I guess Simran was late)

Sample problem 2

Your going to a skiing hill in Geneva...and you decide to go down "The Hill of Terror". You finish the hill in a record 3 minutes (without breaking a bone might i add)at a speed of 76km/h . What was the total distance you travelled?

Step 1: State the given information

_{d =
?

t = 3 minutes =
3min x 1/60 = 0.05 hours}
V_{av = 76Km/h}

Step 2. State the question and modify the equation when needed

V_{av = d/t} (we need to find _{d so we must re arrange the equation)}
_{d =
V}avt

Step 3: Answer the question filling in the given information into equation.

_{d =
76km/h x 0.05 hours}
_{d = 3.8
km}

Step 4: Write the answer in sentence form

Therefore you travelled a total of 3.8 km in 3 minutes down the "The Hill of Terror".

Sample problem 3

A base ball player runs the 50m bases at a speed of 30km/h after hitting a home run. In how much time did he do this?

Step 1: State the given information

_{d =
50m

t =} ?
V_{av = 30 m/h}

Step 2. State the question and modify the equation when needed

V_{av = d/t} (we need to find _{t so we must rearrange the equation)}
_t=V_av/_d

Step 3: Answer the question filling in the given information into equation.

_t=30m/h / 50
_t=1.7hours

Step 4: Write the answer in sentence form

The player ran 50m in 1.7 hours. What can he say he was joyeous he finally hit a home run that we walked the bases....very slowly.

Continue to the next lesson: ::Distance - Time Graphs::