Motion Distance Displacement Speed Velocity Calculating speed and velocity Distance/Time graph What is motion? How can two people see the same object but.

Motion Distance

DisplacementSpeed

VelocityCalculating speed and velocity

Distance/Time graph

What is motion? How can two people see the same object but only one person describe the object

as moving? How can you tell if something is moving? Can you

determine the speed of moving objects?

Lets find out……..

Topics

Covered

Is she moving clockwise orcounterclockwise?

Are the blue dots moving?

At first it may appear that the blue dots are moving. Find a blue dot and concentrate only on that dot. Does everything appear to stop? Was

anything even moving to begin with?

Relative Motion• To describe motion we can ask, “has the object changed

positions?”• In order to explain motion accurately you must first have a

frame of reference aka reference point.Frame of reference-objects not moving in relation to one

another.Relative motion- movement in relation to a frame of reference.What is moving in this slide, the bow or the violin? In which direction is the object moving? Which of the two would be the frame of reference?

Distance vs Displacement Distance is the length of a path

between two or more points (total path travelled)

Displacement is the length from the starting point to the ending point (shortest route from start to finish)

SI (Standard International) Unit= (m) Meters

130 m30 m

What is the total distance travelled by the ambulance?

What is the displacement?

If the distance is the total path travelled and the ambulance went east 50m then

north 30m then back west for 50m then I would simply add the three paths together

to get the distance 50m+30m+50m=130m

And if the displacement is the shortest path from start to

finish then the displacement will be equal to

30m

Lets think about it………

Displacement will always be equal to zero

when the object return to its

starting position

1. A truck travelled 6 km to the East turned around and travelled 3 km back to the West. Distance?Displacement?2. A truck travelled 6 km to the East turned left and travelled 4 km to the North. Distance?Displacement? (Hint: Use Pythagoras theorem to find the unknown side of a triangle)3. If an object starts and stops at the same position what is the displacement?

9 km3 km

10 km

7.2 km

0

Distance vs Displacement Practice

SPEEDHow do you know how fast something is moving?

• You need two things to figure out how fast something is moving.• Think about the speed limit sign

which is mph• What two things are being

considered here? Distance and Time (SI Unit for time = (s) seconds

Speed Vs Velocity

• Speed is how far something travels in a given amount of time. It only indicates a numerical value. We say that it is a scalar quantity.

Scalar= a quantity that has magnitude only Example 55 mph

• Velocity (V) = the speed & direction an object is moving. We say that it is a vector quantity.Vector= a quantity that has

magnitude & direction Example: 55 mph west

Vectors• Vectors can be indicated by an arrow. The length of the arrow

indicates the magnitude, the point of the arrow indicates the direction.

Figure 1 indicate two objects moving in opposite direction with the same magnitudeFigure 2 indicate two objects moving in the same direction, however object B has a greater

magnitude than object A.

Figure 1 Figure 2

Calculating Speed and Velocity

Speed is the ratio of the distance (d) an object moves to the amount of time (t) it takes to get there.

SI unit is m/s (meters per second)

If a student ran the 50m in 6.5s what is their average speed?V=D/T V=50m/6.5s V=7.69m/s

Average Speed Vs Instantaneous Speed

Average speed - computed for the entire duration of the trip (total distance divided by total time)

Instantaneous speed = measured at a particular instant (selected distance divided by corresponding time interval)

Look at the graph to the right and determine:Average Speed=Instantaneous speed at 5 meters=

1 m/s0.625 m/s

Speed and Velocity Practice

1. Mary went on a trip to the beach. She traveled 45 kilometers North in 0.5 hour, followed by 63 kilometers North in 0.7 hour. What was her average velocity?

2. The cross country team runs 5 kilometers in 48 minutes, then 3 kilometers in 36 minutes, and finally 1 kilometer in 16 minutes. What is the average speed for the cross country team in kilometers per minute?

3. If an Olympic swimmer can swim at an average speed of 2.16 meters per second during a 50 meter race, what will their finishing time be?

90 km/hr North

0.09 km/min

23.1 s

Quick Review

1. What is a reference point?

2. What is the SI unit for speed and velocity?

3. What two things do you need to calculate speed?

4. What is the difference between speed and velocity?

An object that is not moving in relation to another

Meters per second (m/s)

Distance and Time

Speed is a numerical value alone and velocity indicates a numerical value and a direction.