Motion

Objectives

• Define motion.

• Calculate the speed of a moving object.

• Distinguish between velocity and acceleration.

Begin

• How do you feel when you are standing on a stopped bus and then the bus begins to move? Why?

Motion

• The change in position of an object as compared with a reference point.

Reference Point

• A location to which you compare to other locations

Question

• Car A is going 45 mph in the left lane. Car B is going 45 mph in the right lane directly along side car A. Is car B in motion relative to car A? Explain.

Relative Motion

• http://www.classzone.com/books/ml_science_share/vis_sim/mfm05_pg7_relmotion/mfm05_pg7_relmotion.html

Not All Motion Is the Same

• All motion is not the same.

Activity• Differentiate between the

motion of a baseball and a jet.

Distance

• The length of the actual path traveled by an object.

• A car travels 50 km.

• A baseball travels 60 feet and 6 inches.

Activity

• Restate the definition of distance in your own words and give an example of distance. Write your answer in your notes.

Speed• The distance an object travels

in a given amount of time.

• A car travels 50 km in one hour.

• A baseball travels 85 miles per hour.

Calculating Speed

• The formula R=D/T is used to calculate speed.

• R is speed (or rate), d is distance, and t is time.

Activity

• If a runner runs 100 meters in 50 seconds, what is his speed in meters per second?

• How far could this runner run in 40 seconds?

Velocity

• Speed in a definite directiondefinite direction.

• 65 km/hour describes speed.

• 65 km/hour north describes velocity.

Velocity

• Two objects can have the same speed but have different velocities.

• 70 mph north and 70 mph south.

Acceleration

• Acceleration is a change in velocity in a period of time.

Which of the Following Are Examples of Acceleration?

• A car stops at a stop light.

• A car goes from 0 to 45 mph.

• A car races around an oval track at a constant speed.

Acceleration

• Acceleration is any change (speed or direction) in an objects motion.

• Acceleration can be negative.

Acceleration of Objects in Free Fall

• The acceleration of an object in free fall on earth is 9.8 m/s2.

• This means that in each second the speed of the object will increase by 9.8 m/s2.

Calculating Acceleration

• Use the following formula:

A= Vfinal-Vinitial

________________

tA= acceleration

V= velocity

T= time

Calculating Acceleration

• John starts sliding with a velocity of 1 m/s. After 3 s, his velocity is 7 m/s. What is John’s acceleration?

Review

• What is the difference between speed and velocity?

• A train travels 85 km in 1.5 hours. What is the speed of the train?

Review

• What is the difference between velocity and acceleration?

• If the moon travels at a constant speed around the earth, would the moon’s velocity also be constant? Why?