Motion Speed Velocity and Acceleration.ppt

Physics basic lesson on motion

1. Motion, Speed, Velocity Motion, Speed, Velocity
and Accelerationand Acceleration

2. VECTORS AND SCALORSVECTORS AND SCALORS
ORIGIN - POINT AT WHICH BOTH VARIABLES ORIGIN - POINT AT WHICH BOTH VARIABLES
ARE AT 0 (ZERO)ARE AT 0 (ZERO)
MAGNITUDE – SIZEMAGNITUDE – SIZE
VECTORS – DIRECTION (represented by VECTORS – DIRECTION (represented by
arrows)arrows)
SCALARS – QUANTITIES W/OUT DIRECTION SCALARS – QUANTITIES W/OUT DIRECTION
(ex distance m, time s, temp C) (ex distance m, time s, temp C)

3. RESULTANT – SUM OF VECTORSRESULTANT – SUM OF VECTORS
6m east plus 2 m east = 8m east6m east plus 2 m east = 8m east
►Resulatant subtracting vectorsResulatant subtracting vectors
►A - B = A+(-B)A - B = A+(-B)
A = 20 m westA = 20 m west
B = 5 m eastB = 5 m east
15m15m

4. Time Interval/DisplacementTime Interval/Displacement
►Time interval - change in time =final time Time interval - change in time =final time
–initial time ….–initial time ….
►formulaformula
►Displacement - Change in distance = final Displacement - Change in distance = final
distance – initial distancedistance – initial distance
►formulaformula

5. MotionMotion
►MotionMotion – an object’s change in position – an object’s change in position
relative to a reference pointrelative to a reference point

6. Reference PointReference Point
►The Earth’s surface is used as a common The Earth’s surface is used as a common
reference pointreference point
►A moving object can be used as a A moving object can be used as a
reference point as wellreference point as well

7. SpeedSpeed
►SpeedSpeed is the distance traveled divided by is the distance traveled divided by
the time interval during which the motion the time interval during which the motion
occurredoccurred
►Normally, objects do not travel at a Normally, objects do not travel at a
constant speedconstant speed
►Average Speed - Average Speed - total distancetotal distance
total timetotal time

8. Which Distance?Which Distance?
►Farmer Jones drives 6 miles down a straight Farmer Jones drives 6 miles down a straight
road. he turns around and drives 4 miles back. road. he turns around and drives 4 miles back.
What was his average speed for this trip if it What was his average speed for this trip if it
took 1 hour?took 1 hour?

  
                                          
 
             

9. Your answer to this problem Your answer to this problem
depends on your interpretation of depends on your interpretation of
"distance traveled". You could say:"distance traveled". You could say:
►The The total distancetotal distance traveled by Farmer Jones is 10 traveled by Farmer Jones is 10
miles. Therefore his average speed is 10 mi/hr. miles. Therefore his average speed is 10 mi/hr.
►The The net distancenet distance traveled by Farmer Jones is 2 miles. traveled by Farmer Jones is 2 miles.
Therefore, his average speed is 2 mi/hr. Therefore, his average speed is 2 mi/hr.
►There are good reasons to use either interpretation - There are good reasons to use either interpretation -
it's mostly a matter of preference. We will interpret it's mostly a matter of preference. We will interpret
"distance traveled" to be "distance traveled" to be net distancenet distance ( (also calledalso called
displacement).displacement). Farmer Jones' average speed was 2 Farmer Jones' average speed was 2
mi/hr.mi/hr.

10. VelocityVelocity
►VelocityVelocity is the speed of an object in a is the speed of an object in a
particular directionparticular direction
►Imagine two birds leave the same tree at Imagine two birds leave the same tree at
the same time. The both fly at 10km/hr the same time. The both fly at 10km/hr
for 5 minutes. Why don’t they end up at for 5 minutes. Why don’t they end up at
the same place?the same place?

12. VelocityVelocity
►VelocityVelocity appears to be very similar to appears to be very similar to
speed, however, when describing the speed, however, when describing the
velocity of an object you need to provide velocity of an object you need to provide
a magnitude and a directiona magnitude and a direction
►MagnitudeMagnitude – the speed of the object – the speed of the object
►DirectionDirection – the direction the object is – the direction the object is
movingmoving
►Pg 43 demoPg 43 demo

13. VelocityVelocity
►Ex) A bus has a velocity of 35miles/hr Ex) A bus has a velocity of 35miles/hr
heading westheading west

14. Resultant VelocityResultant Velocity
►An object can have a resultant velocity if it An object can have a resultant velocity if it
is experiencing more than one motion.is experiencing more than one motion.
►For example if a person walks down the For example if a person walks down the
center of a bus while it is in motion there center of a bus while it is in motion there
are two velocities occurring.are two velocities occurring.
1. The movement of the bus1. The movement of the bus
2. The movement of the person inside the 2. The movement of the person inside the
busbus

15. ExampleExample
15 m/s
+ 1 m/s = 14 m/s

16. ExampleExample
15 m/s
+ =
1 m/s 16 m/s

17. AccelerationAcceleration
►AccelerationAcceleration is the rate at which velocity is the rate at which velocity
changes over timechanges over time
An object accelerates if its speed, direction, or An object accelerates if its speed, direction, or
both changeboth change
►Average acceleration =
final velocity – starting velocity
time it takes to change velocity

18. AccelerationAcceleration
►ExampleExample
A car on the highway is traveling 55 mi/hr A car on the highway is traveling 55 mi/hr
and it passes another car. In order to pass, and it passes another car. In order to pass,
the car has to accelerate to 65 mi/hr. The car the car has to accelerate to 65 mi/hr. The car
reaches this velocity 40 seconds later. What reaches this velocity 40 seconds later. What
is the average acceleration of the car?is the average acceleration of the car?

19. Acceleration and VelocityAcceleration and Velocity
►As velocity As velocity increasesincreases, so does , so does
accelerationacceleration
►As velocity As velocity decreasesdecreases, so does , so does
accelerationacceleration
►When direction changes, so does When direction changes, so does
accelerationacceleration
►When there is a When there is a constant velocityconstant velocity, there , there
is no accelerationis no acceleration