Uniform MotionUniform Motion

Uniform MotionUniform Motion

Uniform = “Constant”Uniform = “Constant” Neither the speed nor direction can change.Neither the speed nor direction can change.

DirectionDirection: must be moving in a straight line, : must be moving in a straight line, forward or back OR up or down.forward or back OR up or down.

SpeedSpeed: can not be speeding up or slowing : can not be speeding up or slowing down.down.

SpeedSpeed A term used to describe motion.A term used to describe motion. Average speedAverage speed is the distance an object is the distance an object

moves in a certain length of time.moves in a certain length of time. Speed = ∆ distance ÷ ∆ timeSpeed = ∆ distance ÷ ∆ time Speed is a scalar quantity so it has only Speed is a scalar quantity so it has only

magnitude (a number and units) and magnitude (a number and units) and does not include direction.does not include direction.

Instantaneous speedInstantaneous speed is the speed at a is the speed at a specific instant in time. specific instant in time.

Q: When would you use average speed?Q: When would you use average speed?

A: When discussing the pace you were travelling A: When discussing the pace you were travelling during a trip. Ex. It took me one hour to drive to during a trip. Ex. It took me one hour to drive to Truro 100 km away, so my average speed was Truro 100 km away, so my average speed was 100 km/h.100 km/h.

Q: What instrument in your car measures Q: What instrument in your car measures instantaneous speed?instantaneous speed?

A: Speedometer.A: Speedometer.

Q: When does instantaneous speed matter?Q: When does instantaneous speed matter?

A: When you are passing a police officer using a A: When you are passing a police officer using a speed gun, which measures your speed at a speed gun, which measures your speed at a specific instant. specific instant.

VelocityVelocity

Velocity describes an object’s Velocity describes an object’s displacement during a specific time displacement during a specific time interval.interval.

Velocity is a vector quantity.Velocity is a vector quantity. Velocity has both magnitude and Velocity has both magnitude and

direction. direction. Ex. 56 km/h West OR -9.8 m/s Ex. 56 km/h West OR -9.8 m/s

Constant and Average Constant and Average VelocityVelocity

When an object travels at the same When an object travels at the same speed and the same direction for a time speed and the same direction for a time interval, it has interval, it has constant velocity.constant velocity.

Average velocity: Average velocity: the displacement of an object divided by the time interval it takes to travel the displacement.

Speed GraphSpeed Graph

Also called Distance-Time GraphAlso called Distance-Time Graph Distance is on the “y” axis.Distance is on the “y” axis. Time is on the “x” axis.Time is on the “x” axis. The slope of the line (how steep it is) is The slope of the line (how steep it is) is

the speed.the speed.

Graph shapes of uniform Graph shapes of uniform motionmotion

Uniform or Non-Uniform?Uniform or Non-Uniform?

Non-uniformNon-uniform

UUniformniform

The position-time graph The position-time graph that represents "uniform that represents "uniform motion" is:motion" is:

AA

Slope orSlope or“Speed”“Speed”

Rise ÷ RunRise ÷ Run ““Rise” (y-axis) is yourRise” (y-axis) is your

change in distancechange in distance

(how far you went)(how far you went) ““Run” (x-axis) is your Run” (x-axis) is your

change in timechange in time

(how long it took)(how long it took)

Step 1:Step 1: Pick two Pick two

points on the graphpoints on the graph

Step 2:Step 2: Write down Write down

the coordinates andthe coordinates and

label (xlabel (x11, y, y11) (x) (x22, y, y22))

Step 3:Step 3: Calculate the Calculate the

rise (yrise (y22 – y – y11))

Step 4:Step 4: Calculate the Calculate the

run (xrun (x22 – x – x11))

Step 5:Step 5: Divide the rise Divide the rise

(∆y) by the run (∆x)(∆y) by the run (∆x)

*

* (9:30, 40km)

(11:30, 200km)

Rise = (y2 – y1)Rise = (200 – 40)Rise = 160 km

(x1, y1)

(x2, y2)

Run = (x2 –x1)Run = (11:30-9:30)Run = 2 hours

Speed = Rise / RunSpeed = Rise / RunSpeed = 160 km / 2 hrSpeed = 160 km / 2 hrSpeed = 80 km/hrSpeed = 80 km/hr

Calculate the speed.Calculate the speed.Speed = d/t or rise/runSpeed = d/t or rise/runSpeed = (5000 – 1000) ÷ (200 – 40)Speed = (5000 – 1000) ÷ (200 – 40)Speed = 4000 m ÷ 160 sSpeed = 4000 m ÷ 160 sSpeed = 25m/sSpeed = 25m/s

(40, 1000)

(200, 5000)

11stst: Constant speed to the right. : Constant speed to the right. ∆∆d = 60m – 0 m; ∆d = 60m d = 60m – 0 m; ∆d = 60m ∆∆t = 10s – 0s; ∆t = 10s t = 10s – 0s; ∆t = 10s Speed = ∆d / ∆t; Speed = 60m/10s; Speed = 6m/sSpeed = ∆d / ∆t; Speed = 60m/10s; Speed = 6m/s22ndnd: Stationary (not moving).: Stationary (not moving). 33rdrd: Constant speed to the left (straight line): Constant speed to the left (straight line)∆∆d = -40m – 60m; ∆d = 100md = -40m – 60m; ∆d = 100m∆∆t = 40s – 15s; ∆t = 25st = 40s – 15s; ∆t = 25sSpeed = ∆d / ∆t; Speed = 100m/25s; Speed = 4m/sSpeed = ∆d / ∆t; Speed = 100m/25s; Speed = 4m/s 44thth: Constant speed to the right (straight line): Constant speed to the right (straight line)∆∆d = 0m - -40m; ∆d = 40md = 0m - -40m; ∆d = 40m∆∆t = 60s – 40s; ∆t = 40st = 60s – 40s; ∆t = 40sSpeed = ∆d / ∆t; Speed = 40m/20s; Speed = 2msSpeed = ∆d / ∆t; Speed = 40m/20s; Speed = 2ms