Physics Motion, Speed, and Velocity SC Standards Covered PS-5.1 Explain the relationship among...
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Transcript of Physics Motion, Speed, and Velocity SC Standards Covered PS-5.1 Explain the relationship among...
PhysicsPhysics
Motion, Speed, and Velocity
SC Standards Covered
PS-5.1 Explain the relationship among distance, time, direction, and the velocity of an object
PS – 5.2Use the formula v=d/t to solve problems related to average speed or velocity
PS – 5.6Represent linear motion of objects on distance – time graphs
Motion
• When an object changes its position, motion has occurred.– Distance- How far an object has moved.– Displacement- How far an object has moved in
relation to its starting point.– Consider direction
Example: Two runners travel along the same straight path in a straight line for 500 meters. At the end of the run their distances are the same but their displacements are different. How can this be so?
Speed- Distance an object travels per unit of time
Relationships between speed, distance, and time:
Speed = Distance/ Time = d/ t » Constant Speed- speed does not change
over time» Average Speed- speed of motion when
speed is changing
Avg Speed = Total Distance/ Total Time
» Instantaneous Speed- speed at any given moment in time (speedometer)
Speed
• The units for speed: • meters/second (m/sec) • kilometers/hour (km/hr)• Speed that does not change is constant speed
Graphing Motion
• Graph distance on the y-axis and time on the x-axis
Slope = rise = distance = speed run time
Distance - Time Graph
• If something is not moving, a horizontal line is drawn.
• If something starts out slow and then speeds up, its change in speed can look like this.
Learning Checkpoint
This graph shows several stages of motion:
• Stage 1: 100 m in 10 s
• Stage 2: 50 m in 10 s
• Stage 3: 150 m in 20 s
Calculate the speed as indicated by each of the colors.
Calculate the average speed.
What is the total distance?
What is the displacement?
Solution
Stage 1: S= d/ t100 m/ 10 s= 10 m/s
Stage 2: S= d/t50 m/ 10 s= 5 m/s
Stage 3: S= d/t150 m/ 20 s= 7.5 m/s
Ave Speed= Tot d/ Tot t300 m/ 40 s= 7.5 m/s
Distance = 300 metersDisplacement = 0 meters
Velocity
• The speed and direction of an object’s motion.–88 km / hr southwest
Acceleration
• The change in velocity• Acceleration is measured in m/sec/sec or m/sec2
• Formula is:• (final velocity - original velocity)/time
Deceleration vs. Acceleration
• A decrease in velocity is deceleration or negative acceleration
• A distance-time graph for acceleration is always a curve
Centripetal Acceleration
• Acceleration directed toward the center of circular path
Frames of Reference
• The object or point from which movement is determined
• Movement is relative to an object that appears stationary
• Earth is the most common frame of reference