Motion Physics

Picturing Motion  How do you know an object is moving?

Picturing Motion  Depends on your frame of reference (f.o.r.) f.o.r. is “one’s point of view”

F.O.R  Example: Motion of the planet of Mars  Earth’s f.o.r. (w.r.t. “with respect to” Earth)

F.O.R.  Sun’s f.o.r. (w.r.t. sun)

F.O.R  Scenario: A car is driving down the road with 2 people standing on either side of the road. One person says the car is going left and the other person says that the car is going right. Who is correct?

F.O.R.  How could we change this picture so that both people agree on the motion of the car?

Reference Point  Reference Point: place or object used for comparison to determine the change in position of an object

Reference Point  Ex. You are sitting at your desk and your reference point is the ground. Are you moving relative to your reference point?  If your reference point becomes the sun, are you moving relative to your reference point?

How do you show motion? 1) Motion Diagram - Series of images of a moving object that shows its position after equal intervals of time

How do you show motion? 2) Particle model - Replacing an object with a single point Example: - Constant speed: - Speeding up: - Slowing down:

Motion Flip Book (12 pts.) Directions: - Cut one piece of card stock into 12 equal pieces - Keep 1 object stationary (reference point) - Have a different object moving (w.r.t.) stationary object - Add some color and be creative - Hint: lay out all 12 pieces 1st - Cut a corner and flip

Motion Terms  Kinematics: the study of motion and how to describe it  Scalar: physical quantity that tells you the amount of something Mass, speed, time, distance

Motion Terms  Vector: physical quantity that tells you the amount and direction of something Velocity, acceleration, force, displacement

Vector  Represented by arrows  Size of arrow gives you magnitude of a quantity  Arrow points in the direction of the motion  Ex. object speeding up

Motion Terms  Coordinate System: tells the zero point of the variables (origin) and in which direction the values increase

Motion Terms  Position: location with respect to the origin  Distance: total length of travel

Motion Terms  Displacement  d = d f – d i d f : final distance from origin d i : initial distance from origin Can be a negative value if d f < d i

Displacement vs. Distance Scenario: You walk from point B to point C, then you return back to point B. What is your distance? What is your displacement? (A is the origin) 2.1 miles4.3 miles A B C 0

Distance vs. Displacement  Distance = 4.3 mi mi = 8.6 mi  Displacement = d f – d i = 2.1mi – 2.1 mi = 0

Displacement vs. Distance Scenario: You walk from point B to point C, then you walk back to point A. What is your distance? What is your displacement? (A is the origin) 2.1 miles4.3 miles A B C 0

Distance vs. Displacement  Distance: 4.3 mi mi mi = 10.7 mi  Displacement: d f – d i = 0 – 2.1mi = mi