*Speed and VelocityWhat is speed, velocity and acceleration?

How does speed, velocity and acceleration relate to Forces & Motion?

*How does MOTION relate to POSITION and TIME?Description of MOTION often includes speed and is a change in position.

SPEED then is the rate of change in position or the rate of motion.QUESTION:Do you have to see something move to know that motion has taken place?

ANSWER:No because the only thing needed is a reference point to see that something has changed position.

*Pretend you are looking at your car's speedometer while you are driving. The reading you get from your speedometer isThis is the speed that you are traveling at that moment.instantaneous speed.Measures of Speed

*Now, lets say you are on a highway, a car may travel at the same speed for a long period of time this would beconstant speed.This is the speed that does not vary cruise control.

*Now, lets say that you are trying to determine the distance you are going to traveled in a given amount of time by the time this would be average speed.Speed is the distance traveled per unit of time.

*Distance, Speed and Time is shown in the equation:Calculating Speed...or shortened:s = Speedd = Distance t = Time

*Manipulating the Equation

*Four Step Approach to Solving ProblemsStep 1 Read the problem. Draw a picture.Step 2Write down what you know. What are you trying to find?Step 4Substitute the numbers. Solve. Box Answer with UNITS!Step 3Set up the formula.

*A car traveled 110 miles in 2 hours.Consider the problemStep 1 Read the problem. Draw a picture.

*d =t =s =110 miles2 hoursStep 2Write down what you know. What are you trying to find?

*A car traveled 110 miles in 2 hours.d =t =s =FormulaSubstituteAnswerUnits, units, units!110 miles2 hoursStep 3Set up the formula.

*A car traveled 110 miles in 2 hours.d =t =s =FormulaSubstituteAnswerUnits, units, units!110 mi2 hoursStep 4Substitute the numbers. Solve. Box Answer with Units.

*Do the problems 1-3 on your notes.

*A runners average speed during the 10 kilometer race was 20 km/hr. What was his time?Consider the problemd =t =s =FormulaSubstituteAnswerUnits, units, units!Step 1 Read the problem. Draw a picture.10 kmSpeed of runner: 20 km/hr

*d =t =s =FormulaSubstituteAnswerUnits, units, units!10 km20 km/hrStep 2Write down what you know. What are you trying to find?10 kmSpeed of runner: 20 km/hrA runners average speed during the 10 kilometer race was 20 km/hr. What was his time?

*FormulaSubstituteAnswerUnits, units, units!Step 3Set up the formula. A runners average speed during the 10 kilometer race was 20 km/hr. What was his time?d =t =s =10 km20 km/hr10 kmSpeed of runner: 20 km/hr

*FormulaSubstituteAnswerUnits, units, units!Step 4Substitute the numbers. Solve. Box Answer with Units.d =t =s =10 km20 km/hr0.5 hrA runners average speed during the 10 kilometer race was 20 km/hr. What was his time?0.5 hrIf the runners average speed was 20 km/hr during the 10km race, the runners time was 0.5 hours.

*Do the problems 4-5 on your notes.

*You decide to go to Dallas to visit your friends. Your friends tell you that it takes 4 hours to get to Dallas at an average speed of 70 miles per hour. Approximately how many miles is it to their house?Step 1 Read the problem. Draw a picture.Step 2Write down what you know. What are you trying to find?Step 4Substitute the numbers. Solve. Box Answerwith units.Step 3Set up the formula. Units, units, units!d =t =s =280 mi70 mi/hr4 hrIf I drive 4 hours at 40mph, the distance from Houston to Dallas is 280 miles.d = s x td = 70mi/hr x 4 hrd = 280 miles

*Do problem 6 on your notes.

*A distance/time graph makes it possible to see speed.This graph shows how fast the swimmers went during their workout.Which swimmer swam at a constant (the same) speed throughout her workout?Which one stopped during his/her workout?Constant speedStopped here400 meters at 10, 15, & 20 minutesIs a straight line

Chart1

00

400200

800400

1200400

1600400

2000800

24001200

Swimmer 1

Swimmer 2

Time in minutes

Distance in meters

Rate of Swimmers

Sheet1

TimeSwimmer 1Swimmer 2

000

5400200

10800400

151200400

201600400

252000800

3024001200

Sheet2

Sheet3

*Make the speed graph in your notes & answer the questions.

*Instantaneous speed (Reading on your speedometer) and average speed does not involve direction. So, what would involve both speed and direction..

*What is the difference between speed and velocity?55 mi/hr55 mi/hr55 mi/hrAll of these cars had the same SPEED but, different VELOCITIES because they were traveling in different directions.If you change direction, you have changed your velocity and if you have changed your speed, you have changed your velocity. Therefore, any change in speed OR direction is a change in velocity!

*Why is it important to know theVELOCITY of a tornado?

*AccelerationWhat is speed, velocity and acceleration?

How does speed, velocity and acceleration relate to Forces & Motion?Here we are back at the same questions

*Acceleration is defined as the change in velocity over time.

*Types of AccelerationPositive AccelerationVelocity and acceleration are in the same direction.Object SPEEDS up.Negative AccelerationVelocity and acceleration are in opposite direction.Object SLOWS down.

*A go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second 6 seconds later. What was the acceleration of the go-cart?Step 1 Read the problem. Draw a picture.topbottom35 m/s5 m/sIn 6 s

*topbottom35 m/s5 m/s6 sVf =Vi=t =a =FormulaSubstituteAnswerStep 2Write down what you know. What are you trying to find?35 m/s5 m/s6 sFinish:final VelocityStart:initial VelocityA go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second 6 seconds later. What was the acceleration of the go-cart?

*topbottom35 m/s5 m/s6 sVf =Vi=t =a =35 m/s5 m/s6 sFinal VelocityInitial VelocityStep 3Set up the formula.FormulaSubstituteAnswerA go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second 6 seconds later. What was the acceleration of the go-cart?

*Vf =Vi=t =a =35 m/s5 m/s6 s5 m/s2Step 4Substitute the numbers. Solve. Box Answer with Units.5 m/s2A go-cart started from the top of a hill at 5 meters per second. At the bottom of the hill it ended up with a speed of 35 meters per second 6 seconds later. What was the acceleration of the go-cart?The go-cart that traveled from 5m/s to 35 m/s in 6 seconds had an acceleration of 5m/s2.

*Do the problems 7-9 on your notes.