Motion

Motion Object changes position over time compared to a reference point Object that appears to stay in place Reference direction Description of the direction of motion

Reference point and direction Examples include: mountains, buildings, trees, non moving objects Directions are usually describe as North, South, East, West, up, down, forward, backward

Describing Reference Direction Describing can be positive or negative. A plus sign (+) means the direction from the reference point is in the reference direction. Words: toward, to the left, to the right A minus (-) sign means the direction is opposite to the reference direction Words: away from, backwards

Position is a vector A vector is a quantity that has both size and direction. A vector is the position of an object and can be represented by an arrow.

Displacement Displacement is the difference between the initial position and the final position of an object. Sometimes you can use the Pythagorean’s Theorem to solve for this.

Speed Rate at which an object moves Depends on time taken and distance traveled

Changing Speed Constant speed is when an object travels the same distance each second. EXAMPLE: A car on the freeway with cruise control on. Instantaneous speed is the speed at a specific instant in time. EXAMPLE: When a car comes to a stop sign and then starts up again.

Speed Total distance Average speed= Units are in meter per second, miles per hour. Always a distance per time. Total time

Speed Equation Triangle method – this method allows you to see all three different equations in order to solve for speed or distance or time

What is the average speed if you take .5 hr to walk 4000m? Example Problem 1 What is the average speed if you take .5 hr to walk 4000m?

Example Problem 2 If average speed of a car is 100km/hr, how long will it take the car to travel 715 km?

Velocity Rate of change of an object’s position Speed of an object in a particular direction Always includes reference direction Velocity changes as speed or direction changes

Answer Self Check question Pg 110 Which of the following are examples of velocity? 25m/s forward 2)1500 km/h 3) 55 m/h 4) all of the above

Combining Velocities Combine two velocities in same direction by adding for resultant velocity Combine two velocities with opposite direction by subtracting the smaller velocity from the larger velocity for the resultant velocity. Resultant Velocity is in the direction of the larger velocity

Final velocity – starting velocity Time it takes to change velocity Acceleration Rate at which velocity changes Tells you how fast velocity changes Acceleration = Final velocity – starting velocity Time it takes to change velocity

Positive and Negative Acceleration Positive acceleration is when acceleration is increasing Negative acceleration or deceleration is when acceleration is decreasing Note: a change in direction is acceleration even if there is no change in speed