# average speed mrs. martinez sixth grade. welcoming work review what is force? what is force? what is...

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• Welcoming Work ReviewWhat is Force? What is a balanced force? Describe by using arrows to draw a diagram. What is an unbalanced force? Describe by using arrows to draw a diagram. Getting your brain gears turning.What is a distance-time graph? What is Motion? What is the connection between Speed, Distance, and Time?

• ForcesA force is a push or pull that one body exerts on another. A force can cause the motion of an object to change. There are two types of forces:Balanced force one in which the net force is zero.Unbalanced force one in which the net force has a numerical value.

• Forces+ 1 force- 1 forceBalanced ForceNet force = 0+ 1 force- 2 forceUnbalanced ForceNet force = -1+ 1 force+ 1 forceUnbalanced ForceNet force = +2

• Turn and Talk What is motion?

• What Is Motion?Motion is when an object changes place or position. To properly describe motion, you need to use the following:

Start and end position?Movement relative to what?How far did it go?In what direction did it go?

• Motion Re-CapWhen an object changes its position, motion has occurred.Distance- How far an object has moved.Displacement- How far an object has moved in relation to its starting point.Consider directionExample: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?

• SPEEDDescribes how fast an object is moving.

• What Is Speed? Speed is the distance an object travels in a certain amount of time (relationship of all 3)To calculate speed, you use the following formula:Speed (s) =Distance(d) Time (t)

• Speed- Distance an object travels per unit of timeRelationships between speed, distance, and time:Speed = Distance/ Time = d/ t Constant Speed- speed does not change over timeAverage Speed- speed of motion when speed is changingAvg Speed = Total Distance/ Total TimeInstantaneous Speed- speed at any given moment in time (speedometer)

• The 3 formulas for Speed, Time & Distance:Using your W/B write them down without using your notes. Remember them fromthis triangle:Solving for SpeedSolving for TimeSolving for Distance

• DONT REMEMBER HUH? WELL LETS REFRESH THAT MEMORY!http://www.youtube.com/watch?v=9x7hP5LM1UE

• Turn and Talk: What is the Relationship between speed, distance and time? Speed is the distance an object travels in a certain amount of time

• Average Speed =Total distanceTotal time

• WB Time!Lets check out your knowledge! Without using your notes answer:What is the formula for finding speed?

What is the formula for finding time, using distance and speed?

What is the formula for finding distance using speed and time?

• Try thisMrs. Martinez walks home from her sisters house everyday. It takes her 4 minutes and her house is 240 meters away.What is her average speed?

240 meters/ 4 minutes =

60 meters per minute.

• Example Question 1Jane drives at an average speed of 45 mph on a journey of 135 miles. How long does the journey take? To find a time, we need to divide distance by speed. 135 miles 45 mph = 3 hours

• Example Question 2

Chris cycles at an average speed of 8 mph. If he cycles for 6 hours, how far does he travel? To find a distance, we need to multiply speed by time. 8 mph 6.5 hours = 52 miles

• Example Question 3

Nikki has to travel a total of 351 miles. She travels the first 216 miles in 4 hours. (a) What is her average speed for the first part of the journey? To find average speed, we need to divide distance by time. 216 miles 4 hours = 54 mph

• Her average speed is the same for the whole of her journey. (b) How long does the whole journey take? To find time, we need to divide distance by speed.351 miles 54 mph = 6.5 hours

• 15 mins = 025 hourSo: 3 hours 15 mins = 325 hours30 mins = 05 hourSo: 7 hours 30 mins = 75 hours45 mins = 075 hourSo: 2 hours 45 mins = 275 hoursReminder: How to change minutes into a decimal

• First work it out on your paper then show me on your WB. A windsurfer travelled 28 km in 1 hour 45 mins.Calculate his speed.Speed = = 16 km/h1 hour 45 minsAnswer: His speed was 16 km / hour

• 2 hour 30 minsAnswer: He travelled 125 kmA salesman travelled at an average speed of 50 km/h for 2 hours 30 mins. How far did he travel?Distance = Speed x Time= 50 x 25= 125 km

• Answer: It took 9 hours 15 minutesA train travelled 555 miles at an average speed of 60 mph. How long did the journey take?Time == 925 hours= 9 hours 15 mins

• Speed Problem

Suppose you ran 2 km in 10 min. What is your speed?

S = 2 km = 0.2 km/min 10 min

• Ways To Calculate SpeedConstant speed is when you are traveling at the same rate of speed, such as 55 mph constantly on a highway.Average speed is taking the total distance traveled, and dividing by the total time it takes. Used for calculations that involve changing speed.Instantaneous speed is the speed at any one given point in time.

• Sooo What is the formula for speed? http://www.youtube.com/watch?feature=endscreen&v=K_kzgW_OYX0&NR=1

• Practice Question 1 Jim travels 45 miles at 15 mph. How long does it take him?

• 45 miles/15 mph=

3 hrs.

• Practice Question 2 Jemimah walks at 4 mph for 2 hours. How far does she walk?

She walked 10 miles. 4 mph x 2.5 hrs= 10 miles

• Practice Question 3 Jenny drives at a constant speed. In the first three hours she travels 81 miles. How far will she have travelled after 5 hours? She will travel 135 miles27 mph for 5 hrs= 135 miles

• GRAPHING AVERAGE SPEEDUsing a Distance-Time Graph

• Graphing MotionGraph distance on the y-axis and time on the x-axis

Slope = rise = distance = speed run time

• Graphing SpeedSpeed is usually graphed using a line graph, and it depicts the distance and time.Time is the independent variable, and thus is ALWAYS on the x-axis.Distance is the dependent variable, and is ALWAYS on the y-axis.

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• Average SpeedWhat is the AVERAGE speed of the bass boat depicted in the graph?Average Speed = 125 meters = 15.6 m/s 8 seconds

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• Instantaneous SpeedWhat is the instantaneous speed of the bass boat at t=7 seconds?Instantaneous Speed = 85 meters = 12.1 m/s 7 seconds

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• Speed Graphs

In what time period is the bass boat speeding up? In what time period is the bass boat slowing down?When is the speed NOT changing?

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• Distance - Time GraphIf something is not moving, a horizontal line is drawn.If something starts out slow and then speeds up, its change in speed can look like this.

• Learning CheckpointThis graph shows several stages of motion:Stage 1: 100 m in 10 sStage 2: 50 m in 10 sStage 3: 150 m in 20 sCalculate the speed as indicated by each of the colors. Calculate the average speed.What is the total distance?What is the displacement?

• SolutionStage 1: S= d/ t100 m/ 10 s= 10 m/sStage 2: S= d/t50 m/ 10 s= 5 m/sStage 3: S= d/t150 m/ 20 s= 7.5 m/sAvg Speed= Tot d/ Tot t300 m/ 40 s= 7.5 m/sDistance = 300 metersDisplacement = 0 meters

• 3) At a daily basis, you rotate between classes. Draw a distance vs time graph illustrating the distance you travel during class rotations here at school