Calculating Speed: Calculating Speed: In regards to motion, In regards to motion, speedspeed is the distance is the distance traveled within a certain amount of time.traveled within a certain amount of time. The The more distance covered in a shorter amount of more distance covered in a shorter amount of time, the faster the object. Or if the same time, the faster the object. Or if the same distance is traveled in a shorter time, the faster distance is traveled in a shorter time, the faster the object. Speed is calculated using the the object. Speed is calculated using the following formula:following formula:

Speed = Distance ÷ TimeSpeed = Distance ÷ Time

Time and Distance can also beTime and Distance can also be determined using the triangle determined using the triangle

Time = Distance ÷ Time Time = Distance ÷ Time Distance = Speed x TimeDistance = Speed x Time

÷ ÷

x

Speed UnitsSpeed UnitsDistance:Distance: Time: Time: Speed: Speed:

CommoCommon Unitsn Units

Meters (m)Meters (m)

Kilometers Kilometers (km)(km)

Miles (M) Miles (M)

Seconds Seconds (sec)(sec)

Hours Hours (hr) (hr)

Meters/Sec Meters/Sec (m/s)(m/s)Kilometers/Kilometers/HourHour (km/hr)(km/hr)

Miles/Hour Miles/Hour (M/hr) (M/hr)

To know which units to record, always look in the problem!

Interpreting GraphsInterpreting Graphs• In this graph, Time is the In this graph, Time is the

independent variable independent variable • An An independent variableindependent variable is a is a

variable that isn’t changed by variable that isn’t changed by other variables you are trying other variables you are trying to measureto measure

• This means that time changes This means that time changes “independently” of the “independently” of the distance covereddistance covered

• Distance is the dependent Distance is the dependent variable. variable.

• A A dependent variabledependent variable is a is a variable that changes, variable that changes, depending on the independent depending on the independent variablevariable

• The distance covered is The distance covered is “dependent” upon the amount “dependent” upon the amount of time that has passedof time that has passed

Which student is moving faster?

How can you tell?

• Constant Speed: Constant Speed: a speed that does not a speed that does not changechange

• The graph below shows the motion of a The graph below shows the motion of a remote control car. The car is moving at a remote control car. The car is moving at a constant speed. You can tell because if you constant speed. You can tell because if you calculate the speed at any point on the calculate the speed at any point on the graph, it will always be the same.graph, it will always be the same.a. What is the speed after 1 a. What is the speed after 1

second? second?

b. What is the speed after 3 b. What is the speed after 3 seconds?seconds?

c. What is the speed after 5 c. What is the speed after 5 seconds?seconds?

Describe the line on the graph.

• Average Speed:Average Speed: • The graph below shows a bicyclist’s journey. The graph below shows a bicyclist’s journey.

The graph does not show a continuous The graph does not show a continuous straight line, therefore this object is not straight line, therefore this object is not moving at a constant speed. moving at a constant speed. You can calculate You can calculate the average speed, however, by dividing the the average speed, however, by dividing the total distance by the total time.total distance by the total time.

• Average speed = Average speed =

Total Distance ÷ Total TimeTotal Distance ÷ Total Time AS =

Calculate Average Speed: Calculate Average Speed: • You are on a trip to Florida. Within the You are on a trip to Florida. Within the

first 2 hours, you travel 50 miles. Over first 2 hours, you travel 50 miles. Over the the next next 3 hours, you travel an 3 hours, you travel an additionaladditional 195 miles. What is your 195 miles. What is your average speedaverage speed?? AS =

Brain Pop:Brain Pop:

• http://www.brainpop.com/science/mhttp://www.brainpop.com/science/motionsforcesandtime/acceleration/otionsforcesandtime/acceleration/