Motion Speeding Forward

Motion Motion: A change in position, measured by distance & time.

Reference Point A reference point is a place or object used for comparison to determine if something is in motion. An object is in motion if it changes position relative to a reference point Some point must be considered as nonmoving. The Earth is the most common reference point.

Relative Motion All Motion is Relative. Whether or not an object is in motion depends on the reference point.

Speed Speed is the distance the object travels per unit of time. Speed is a type of rate Speed only gives distance & time Ex. 60 km/hour

Calculating Speed To calculate the speed of an object, divide the distance the object travels by the amount of time it takes to travel that distance. Speed= Distance / Time Distance= Time times Speed Time= Distance/Speed

Average Speed Speed of most moving objects is not constant. Average Speed is total distance (d) traveled divided by the total time (t).

Average Speed Example Total distance = 36 miles + 24 miles = 60 miles Total time = 3 hours + 1 hour = 4 hours Average speed (v) = d = 60mi t 4 = 15 mph

Velocity Velocity is speed in a given direction. Velocity gives distance, time and direction of travel. Ex. 50 miles/hour to the west Changes in velocity may be due to changes in speed, changes in direction or both.

Toy Soldier March Distance In Cm # of Turns (independent var.)

Wind up Toy Data Table Trial Number of Turns Distance Traveled Trial 1   Trial 2 Trial 3

Speed of Battery Operated Car 1 2 3 4 5 6 7 Total Distance Time Trial #1 Time Trial #2 Time Trial #3 Avg time Speed Fraction Average speed for each 100 cm (Cm) (S) (Cm/s) 0.00 0/00 ---- 100 200 300 400 500 600

Battery Powered Car Lab Distance vs. Time Graph Distance in Cm Time in seconds

Changing Velocity Acceleration is the rate at which velocity changes with time. In science, acceleration refers to increasing speed, decreasing speed or changing direction. Like displacement and velocity, acceleration is a vector with a magnitude and a direction.

Increasing Speed Whenever an object’s speed increases, the object accelerates.

Decreasing Speed Just as objects can speed up, they also slow down, this is called deceleration or negative acceleration.

Calculating Acceleration To determine the acceleration of an object, you must calculate its change in velocity per unit of time. Acceleration = Final velocity – Initial velocity Time

Distance – Versus – Time Graph You can also show the motion of an accelerating object with a distance – versus – time graph.

Accelerated Motion Matchbox Car Lab Di stance In cm Time in Seconds

Students Car Trial Distance (m) Time (sec) Speed (m/s)   1 0.6 2 3 Average 1.2 1.8 2.4 1.20 0.5 1.35 0.4444444 1.27 0.4724409 1.273333 0.4722951 1.70 0.7058824 1.65 0.7272727 1.72 0.6976744 1.69 0.7102765 1.83 0.9836066 1.85 0.972973 1.84 0.9782609 0.9782801 2.00 2.10 1.1428571 2.05 1.1707317 1.1711963

References http://middleschoolnotes.org/science/physical-science/outlines/chapter-9- motion-and-energy.php