Linear Motion To study motion, we need to break it down. 1. As the car drives down the road, Earth is spinning on it’s axis, therefore the car is spinning around the axis. 2. Earth is also revolving around the sun. 3. The sun and solar system is moving through our galaxy. 4. Our galaxy is moving through space.

Linear Motion One way to break the motion into simpler parts is to use a frame of reference. Frame of reference = an object against which you can measure changes in position. Ex: A gas station along the road can be a frame of reference for motion of a car. When you pick a frame of reference it remains fixed for the problem and has a starting point from which the motion is measured.

Linear Motion If an object is at rest (not moving) its position does not change with respect to the frame of reference. Ex: The pumps at the gas station are not moving with respect to the gas station.

Linear Motion As an object moves from an initial (starting) position to it’s final position, the length of the straight line drawn from its initial position to the object’s final position is called its displacement. Displacement = the change in position of an object.

Linear Motion Displacement can be positive or negative. Convention says: to the right (east) is positive to the left (west) is negative upward (north) is positive downward (south) is negative.

Linear Motion Δx = xf - xi Δx = 85cm – 25 cm Δx = 60 cm What would the displacement be if the lizard was lined up on the 0 cm mark?

Linear Motion

Velocity Speed is the distance traveled in a time interval. Ex: A runner goes 5.0 km in 25 minutes. Velocity is distance in a direction in a time interval. Velocity is speed in a direction. Ex: A car drives north for 10 km in 5 minutes. Average velocity (vavg ) is defined as the displacement divided by the time interval during which the displacement occurred.

Velocity So, average velocity = change in position Change in time Remember that a change in position has a DIRECTION! Vavg = Δ d = df – di Δt = tf – ti Average velocity can be positive or negative.

Velocity Ex: During a race on level ground, Mr. Dickson runs with an average velocity of 6.02 m/s to the east. What is his displacement after 137 s? Given: Vavg = 6.02 m/s Δt = 137 s Unknown: Δd = ? Equation: Vavg = Δd / Δt  Δd = Vavg * Δt Substitute: Δd = (6.02 m/s)*(137 s) Solve: Δd = 825 m to the east