Warm-Up

Kinematics: the study of motion

• Take out a sheet of paper and answer the following questions.

• How do you define “motion”?

• What do we need to know in order to define “motion”?

Kinematic ConceptsMotion

• Requires a change in distance/displacement

• Change in distance/displacement must occur over a period of time (rate)

Kinematic ConceptsAverage Velocity

• Basic motion = ∆d / ∆t

• Speed is the rate of change of distance– Speed = change in distance over time– Formula:

savg = ∆distance / ∆time

Kinematic ConceptsAverage Velocity

• Basic motion = ∆d / ∆t

• Velocity is rate of change of displacement– Velocity = change in displace over time– Formula:

vavg = ∆displacement / ∆time

Difference Between Scalars and Vectors

• A car is going due north at 60 km/hr.

• Another car is going due south at 60 km/hr.

• Do the cars have the same speed?

• Do the cars have the same velocity?

Difference Between Scalars and Vectors

• In the end, does this sailboat have a displacement?

Different vectors and scalars

• Distance (scalar) vs. Displacement (vector)

• Speed (scalar) vs. Velocity (vector)

• Acceleration (vector)

• Force (vector)

Perfect Physics World

• One model of physics

• No friction or air resistance

Kinematic ConceptsAverage Velocity

• Motion = ∆d / ∆t

• Speed is the rate of change of distance

• Velocity is rate of change of displacement

• Velocity and speed tell you how fast position is changing, not just a change in position.

• Average velocity = ∆d / ∆t

Kinematic Vocabulary

• Average Velocity– Can velocity be higher or lower than average

over the same period of time?

• Instantaneous Velocity– An object’s velocity at a specific moment in

time

• Constant Velocity

“Constant” Velocity Activity

• Bat the ball between your hands.– Try to keep a good rhythm

• Observe the motion of the ball.

• Is there a velocity change?

• Is there a period when velocity doesn’t change much?

Keys to successful word problems

1. Read the problem carefully.

2. What is the question asking?

3. What information does it give us?

4. Draw the problem out.

5. Given the information, which equations can I use?

Kinematic ProblemsSpeed and Velocity

• An ostrich can run at speeds of up to 72 km/h. How long will it take an ostrich to run 1.5 km at this top speed?

Kinematic ProblemsSpeed and Velocity

• Hawaii is formed by the Pacific plate moving Northwest across a hot spot in the Earth’s crusts. As the plate moves new islands form to the Southeast. If Hawaii is 2.24 x 103 km long and the Pacific plates moves at an average speed of 50. mm per year, how many years did it take the plate to move the length of Hawaii?

Kinematic ProblemsSpeed and Velocity

• Jupiter, the largest planet in our solar system, has an equatorial radius of about 7.1 x 104 km (>10 times that of Earth). Its period of rotation, however, is only 9 h, 50 min. Calculate the average speed (in km/hr) of an equatorial point during one period of Jupiter’s rotation. Is the average speed different from average velocity?