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

1A) A Student walks from A to B to C to D and back to A. What distance did the student travel? A.0 meters B.6 meters C.10 meters D.12 meters

1B) A Student walks from A to B to C to D and back to A. What is the student’s displacement? A.0 meters B.6 meters C.10 meters D.12 meters

Distance Vs. Displacement Same direction: ADD Opposite direction: SUBRACT

Vector Diagrams Distance = Vectors are drawn as arrows Vector lines are also labeled E 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 A B C D Displacement =

SCALAR NO direction Example: Distance VECTOR HAS direction Example: Displacement

Speed Speed is 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 v d t

Instantaneous vs. Average Speed Instantaneous Speed The speed at any instant in time. Average Speed Normally, objects do not travel at a constant speed

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—How fast you move!! – Velocity—Speed in a particular direction!! SPEED VS VELOCITY

Solving Word Problems: 1.Write down what you are given(the important stuff like #’s, etc.). 2.Write down what you are looking for! 3.Find an equation that fits what you have. 4.Solve the equation for what you are looking for! 5.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?

Straight Line, therefore constant Velocity!!

Accelerated Motion

Acceleration Defined as a rate of change of velocity. In order to accelerate, an objects’ velocity must change!! ways to change velocity: 1.Speed up. 2.Slow down. 3.Change direction 4.Change in BOTH speed and direction

Which of these pictures represents acceleration? Why??

Which vehicle is accelerating? How can we tell?

Acceleration Equation Where: v f = final velocity(in m/s) v i = initial velocity(in m/s) t = time(in s) a = acceleration(in m/s/s or m/s 2 ) a t v f - v i

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: v i = 5 m/s v f = 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: v i = 0 m/s v f = 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: v i =14 m/s v f = 0 m/s t = 3.5 s a = ? Negative, therefore slowing down!!

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: v i = 10 m/s t = 3 s v f = 32 m/s a = ? WORK : a = (v f - v i ) ÷ t a = (32m/s - 10m/s) ÷ (3s) a = 22 m/s ÷ 3 s a = 7.3 m/s 2 a v f - v i t

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: v i = 0 m/s t = 12 s v f = 6.7 m/s a = ? WORK : a = (v f - v i ) ÷ t a = (6.7m/s - 0m/s) ÷ (12s) a = 6.7 m/s ÷ 12 s a =.56 m/s 2 a v f - v i t

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 : v i = 9 m/s t = 5 s v f = 0 m/s a = ? WORK : a = ( v f - v i ) ÷ t a = (0m/s - 9m/s) ÷ (5s) a = -9 m/s ÷ 5 s a = -1.8 m/s 2 a v f - v i t

Calculations GIVEN: t = ? v i = 30 m/s v f = 0 m/s a = -3 m/s 2 WORK: t = (v f - v i ) ÷ a t = (0m/s-30m/s)÷(-3m/s 2 ) t = -30 m/s ÷ -3m/s 2 t = 10 s a v f -v i t 10) How long will it take a car traveling 30 m/s to come to a stop if its acceleration is -3 m/s 2 ?

When does the slope of a velocity time graph = acceleration? Always, you Clown!!!

The steeper the graph, the greater the acceleration. A horizontal line means the object is moving at a steady speed. A downward sloping line means the object is slowing down. A speed- time graph shows us how the speed of a moving object changes with time.

Acceleration Positive acceleration “speeding up” Negative acceleration “slowing down”

1.Is this object moving? i.Does it have a velocity? 2.What is the objects’ acceleration?