Presentation on theme: "Motion A change in position relative to some reference point during a period of time."— Presentation transcript:
1MotionA change in position relative to some reference point during a period of time.
2Speed Rate at which an object moves Speed = distance/time Units: m/sec, km/hr, mi/hr.ds t
3Types of Speed Instantaneous Speed – speed at a given instant. Average Speed = ∆ distance/ ∆ time. Describes speed of motion when speed is changing.Constant Speed – speed that doesn’t change.
4Speed ProblemsWhat is the speed of a cyclist who travels 50 meters in 25 seconds?S = d/t50 m/25 s2 m/sYou are in a car traveling an average speed of 60 km/hr. The total trip is 240 km. How long does the trip take?t = d/s240 km/60 km/hr4 hrs.
5Distance -Time Graphs Time (sec) Time (sec) Time (sec) Time (sec) Distance (m)Distance (m)Time (sec)Time (sec)Distance (m)Distance (m)Time (sec)Time (sec)
6Velocity Speed in a given direction. Uses: Navigation (airplanes, ships), weather, etc.Vector quantity – represented graphically by arrows ( ).Length = magnitudeArrowhead =direction
7Velocity ProblemIf you row a boat upstream at 10 km/hr and the river has a downstream velocity of 5 km/hr, you are actually moving at what velocity?=5 km/hr downstream10 km/hr upstream5 km/hr upstream
8Acceleration Rate of change in velocity. Really a description of “how fast you can go in a certain amount of time”.Good acceleration is being “quick to change”.
9AccelerationExamples: speeding up (+ acc.), slowing down (- acc.), or changing direction.Acc. = final velocity – original velocity/time.Units: m/sec/secRepresented by a Velocity – Time Graph
10Velocity vs. Time Graphs Time (sec)Velocity (m/s)Time (sec)Velocity (m/s)Time (sec)Velocity (m/s)Time (sec)Velocity (m/s)
11Acceleration ProblemA car increases its speed from 60 km/hr to 80 km/hr in 4 seconds. What is the car’s acceleration?Acc = Δ velocitytime80 km/hr – 60 km/hr4 sec.5 km/hr/sec.1st second – 65 km/hr2nd second – 70 km/hr3rd second – 75 km/hr4th second – 80 km/hr
12Rates of Motion Table Rates Definition Equation Unit Graph Speed VelocityAcceleration
13Gravitational Acceleration Acceleration on an object caused by gravity.
14Falling ObjectsFree fall – considers only gravity & neglects air resistance.All falling objects accelerate at the same rate, regardless of their masses.- 9.8 m/sec/sec or 32 ft./sec/sec. on earth.- velocity increases 9.8 m/s each second.- distance fallen – increases mathematically
15Uniform Motion Equations Instantaneous speed vf = vi + atDistance fallen d = vit + ½at2Average speed v = vi + vf2