CHAPTER 2. Distance vs. Displacement Distance: How far an object has moved I ran 10 meters north and...
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Transcript of CHAPTER 2. Distance vs. Displacement Distance: How far an object has moved I ran 10 meters north and...
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 1st 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?