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.RExample: Motion of the planet of MarsEarth’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

pointExample:- 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 somethingMass, speed, time, distance

Motion Terms

Vector: physical quantity that tells you the amount and direction of somethingVelocity, acceleration, force, displacement

Vector

Represented by arrowsSize of arrow gives you magnitude of a

quantityArrow points in the direction of the motionEx. 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 TermsDisplacement

d = df – di

df : final distance from origin

di : initial distance from origin

Can be a negative value if df < di

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 miles 4.3 miles

A B C

0

Distance vs. Displacement

Distance = 4.3 mi + 4.3 mi = 8.6 mi

Displacement = df – di = 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 miles 4.3 miles

A B C

0

Distance vs. Displacement

Distance: 4.3 mi + 4.3 mi +

2.1 mi = 10.7 miDisplacement: df – di =

0 – 2.1mi = - 2.1 mi