# CHAPTER 2. Distance vs. Displacement Distance: How far an object has moved I ran 10 meters north and 30 meters south. How far did I run? Displacement:

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CHAPTER 2

Distance vs. Displacement Distance: How far an object has moved I ran 10 meters north and 30 meters south. How far did I run? Displacement: How far the object moved from the starting point What is my displacement in the previous problem?

Motion Distance- how far object moved Displacement- distance and direction the object moved from starting location Speed = distance / time (Don’t forget units) Ex: 5 m/s

Speed You travel 10 meters in 2 seconds. What was your speed? Your speed is 100 km/h and you’ve been driving for 5 hours. How far have you driven?

Average vs. Instantaneous Average speed = total d / total t Instantaneous speed = speed at that given second

Trickier problem Sound travels at 330 m/s. If a lightning bolt hits the ground 1 km away from you, how long will it take for the sound to reach you?

Speed vs. Velocity Speed = d / t Velocity = speed of object and direction of its motion

Acceleration Change in object’s velocity (speed and direction of motion) Increasing speed =positive acceleration Decreasing speed = negative acceleration Acceleration = change velocity / time Acceleration = (Vf – Vi) / t Don’t forget units! Ex: 5 m/s^2 Gravitational acceleration 9.8 m/s^2

Acceleration A jet airliner starts at rest at the end of the runway and reaches a speed of 300 m/s in 20 seconds. Calculate the acceleration.

Acceleration again A skateboarder is moving at a speed of 20m/s and comes to a stop in 2 seconds. Calculate the acceleration.

Force Push or pull on an object Gravity is a basic force Closer objects are together, the grav force between them increases

Balanced Force Net force = 0 Same force in opposite directions cancel each other out No movement

Unbalanced Force Unequal forces in opposite directions Movement occurs Net force = # in one direction Centripetal force = unbalanced force, with an object accelerating towards the center

Inertia Tendency of an object to resist a change in its motion Newton’s 1 st Law of Motion: an object moving at a constant velocity or at rest will remain that way unless it is acted upon by a force Why should we wear seatbelts?

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