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What is Motion???. Motion — the movement of an object in relation to frame of reference. Frame of Reference. Motion Terms:. Distance vs. Displacement Distance —How far you move. Displacement —How far you are from where you started!!. 50 m.
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What is Motion??? Motion—the movement of an object in relation to frame of reference.
Motion Terms: • Distance vs. Displacement • Distance—How far you move. • Displacement—How far you are from where you started!! 50 m
1A) A Student walks from A to B to C to D and back to A. What distance did the student travel? 0 meters 6 meters 10 meters 12 meters
1B) A Student walks from A to B to C to D and back to A. What is the student’s displacement? • 0 meters • 6 meters • 10 meters • 12 meters
Same direction: ADD Opposite direction: SUBRACT Distance Vs. Displacement
Vectors are drawn as arrows Vector Diagrams E Vector lines are also labeled Displacement = D C A Distance = B • 1 block East Vector A • 1 block North Vector B • 2 blocks East Vector C • 3 blocks north Vector D • 3 blocks west Vector E
d v t Speed • Speedis the distance traveled divided by the time interval during which the motion occurred • Where: d is distance(displacement)----given in m or km t is time----given in s or hr v is velocity-----given in m/s or km/hr
Instantaneous vs. Average Speed Instantaneous Speed Average Speed Normally, objects do not travel at a constant speed • The speed at any instant in time.
Velocity • Velocity • speed in a given direction • can change even when the speed is constant!
The Velocity Equation: • Where: d is distance(displacement)----given in m or km t is time----given in s or hr v is velocity-----given in m/s or km/hr Same equation used for speed!!!
SPEED VS VELOCITY • Speed vs. Velocity • Speed—How fast you move!! • Velocity—Speed in a particular direction!!
Solving Word Problems: • Write down what you are given(the important stuff like #’s, etc.). • Write down what you are looking for! • Find an equation that fits what you have. • Solve the equation for what you are looking for! • Plug and Chug!!
Solving Speed and Velocity Problems: 1) A person walks 50 m in 12 s. At what velocity did the person travel? Given: d = 50 m t = 12 s s = ? S S S
2) A car is moving down the road at 25 m/s. How far will it travel in 18 s? Given: s = 25 m/s t = 18 s d = ? S S S
3) A whale is swimming across the ocean at 14 m/s. How long will it take the whale to swim 1000 m? Given: v = 14 m/s d = 1000 m t = ? S S
Distance Vs. Time Graphs What can be determined by the slope of a distance time graph?
Acceleration • Defined as a rate of change of velocity. • In order to accelerate, an objects’ velocity must change!! • ways to change velocity: • Speed up. • Slow down. • Change direction • Change in BOTH speed and direction
Which vehicle is accelerating? How can we tell?
vf- vi t a Acceleration Equation Where: vf = final velocity(in m/s) vi = initial velocity(in m/s) t = time(in s) a = acceleration(in m/s/s or m/s2)
4) A police car changes its velocity from 5 m/s to 20 m/s in 4 s. Find the rate of acceleration of the car. Given: vi = 5 m/s vf = 20 m/s t = 4 s a = ?
5) A world class sprinter can accelerate from rest to a velocity of 10 m/s in 1.8 s. Determine the rate of acceleration of the sprinter? Given: vi = 0 m/s vf = 10 m/s t = 1.8 s a = ?
6) While driving down the road at 14 m/s, a dog runs out in the road in front of you. You slam on brakes and come to a complete stop in 3.5 s. Find the rate of acceleration. Given: vi =14 m/s vf = 0 m/s t = 3.5 s a = ? Negative, therefore slowing down!!
vf - vi t a Calculations 7) A roller coaster starts down a hill at 10 m/s. Three seconds later, its speed is 32 m/s. What is the roller coaster’s acceleration? GIVEN: vi = 10 m/s t = 3 s vf = 32 m/s a = ? WORK: a = (vf- vi) ÷ t a = (32m/s - 10m/s) ÷ (3s) a = 22 m/s ÷ 3 s a= 7.3 m/s2
vf - vi t a Calculations 8) A skater goes from a standstill to a speed of 6.7 m/s in 12 seconds. What is the acceleration of the skater? GIVEN: vi = 0 m/s t = 12 s vf = 6.7 m/s a = ? WORK: a = (vf- vi) ÷ t a = (6.7m/s - 0m/s) ÷ (12s) a = 6.7 m/s ÷ 12 s a= .56 m/s2
vf - vi t a Calculations 9) As a shuttle bus comes to a normal stop, it slows from 9.00m/s to 0.00m/s in 5.00s. Find the average acceleration of the bus. GIVEN: vi = 9 m/s t = 5 s vf = 0 m/s a = ? WORK: a = (vf- vi) ÷ t a = (0m/s - 9m/s) ÷ (5s) a = -9 m/s ÷ 5 s a= -1.8 m/s2
vf -vi t a Calculations 10) How long will it take a car traveling 30 m/s to come to a stop if its acceleration is -3 m/s2? GIVEN: t = ? vi = 30 m/s vf = 0 m/s a = -3 m/s2 WORK: t = (vf- vi) ÷ a t = (0m/s-30m/s)÷(-3m/s2) t = -30 m/s ÷ -3m/s2 t = 10 s
When does the slope of a velocity time graph = acceleration? Always, you Clown!!!
A speed- time graph shows us how the speed of a moving object changes with time. A horizontal line means the object is moving at a steady speed. The steeper the graph, the greater the acceleration. A downward sloping line means the object is slowing down.
Acceleration • Positive acceleration • “speeding up” • Negative acceleration • “slowing down”
Is this object moving? • Does it have a velocity? • What is the objects’ acceleration?