chapter 2: motion. compare your maximum speed with that of a cheetah, horse, elephant, and snake....
TRANSCRIPT
Section 1: Describing Motion
Chapter 2: Motion
Warm-up:Compare your maximum speed with that of a cheetah, horse, elephant, and snake. Could you win a race against any of them?
Learning Goals:Distinguish between distance and displacement.
Explain the difference between speed and velocity.
Interpret motion graphs.
Motion and PositionA reference point is needed to determine the position of an object.
Motion occurs when an object changes position relative to its reference point.
Distance and DisplacementDistance: how far an object has moved
Displacement: the distance and direction of an object’s change in position from the starting point The SI unit for distance and displacement is the meter (m).
A runner runs from the start line 50 m north plus 30 m in the opposite direction.
What is the distance?
What is the displacement?
40 meters
40 meters
22 meters
22 meters
SpeedSpeed: the distance an object travels per unit of time
Calculating SpeedSpeed = distance / time
Speed = d/t
Distance measured in meters (m)
Time measured in seconds (s)
Speed measured in meters/seconds (m/s) or kilometers/hour (km/h)
Calculating SpeedSpeed = d/tDistance =Time =
Calculating Speed 1A car traveling at a constant speed
covers a distance of 750 m in 25 s. What is the car’s speed?
Calculating Speed 2A man runs at a speed of 2.30 m/s.
How long does it take for the man to run 50 m?
Calculating Speed 3A car is travelling at 30 km/hr for
125 s. How far does the car travel in meters?
SpeedAverage speed: total distance traveled divided by the total time of travel
Instantaneous speed: speed at a given point in time
40 meters
40 meters
22 meters
22 meters
4 s
11 s
10 s
2 s
Graphing MotionMotion can be
shown on a distance vs. time graph Time on x-axis Distance on y-
axis
Graphing MotionOn a distance vs.
time graph the slope describes the speed Steeper slope =
faster speed Horizontal line = zero
speed = object at rest
Distance (m)
Time (s)
VelocityVelocity: includes the speed of an
object and the direction of its motion
Because velocity depends on direction as well as speed, the velocity of an object can change even when its speed does not!
Car is driving 30 km/hr, but its velocity is constantly changing!
40 meters
40 meters
22 meters
22 meters
4 s
11 s
10 s
2 s
Check-in:Miss Marnik walked a distance of 1.60 km in 30 min. Find her average speed in m/s.