Motion Part 1 Motion and Speed Speed is

Motion Part 1: Motion and Speed

Speed is the distance an object travels per unit of time. To calculate speed: Speed = Distance ÷ Time Distance is in meters (m) Time is in seconds (s) Speed is in meters per second (m/s)

Example 1 A snail takes 5. 0 s to crawl across the ruler. Speed ==Distance 0. 07 = 2. 0 m m/s ÷÷ 5. 0 Time s

Example 2 A car drives 250 m in one minute. Speed = Distance == 250 4. 17 m ÷m/s ÷ 60 Time s

Use the Formula Triangle! d s t To calculate speed: To calculate time: To calculate distance: s=d/t t=d/s d=sxt

Distance vs. Displacement Distance and displacement are different. Distance Displacement How far an object moves in total. The distance and direction an object moves from a starting position.

Distance vs. Displacement Jeffrey, my distance was 176 meters! I G BE N But Billy, your displacement was 1 meter! D EN

Distance vs. Displacement 90 ft. Distance = 90 ft. Displacement = 90 ft.

Distance vs. Displacement 90 ft. Distance = 180 ft. Displacement =127 ft.

Distance vs. Displacement 90 ft. Distance = 270 ft. Displacement = 90 ft.

Distance vs. Displacement 90 ft. Distance = 360 ft. 90 ft. Displacement = 0 ft.

Any Questions?

Motion Part 2: Distance-Time Graphs

Graphing Speed The motion of an object can be graphed. A distance-time graph shows the motion of a certain object in line graph form. Time is plotted on the horizontal (X) axis Distance is plotted on the vertical (Y) axis

Distance-Time Graphs Time (s) Distance (m) 0 0 1 2 2 4 3 6 4 8 5 8 6 8 7 8 8 8 9 12 10 16 The slope of a distance-time graph is the speed

Distance-Time Graphs S=D÷T =0÷ 4 = 0 m/s S=D÷T =8÷ 4 = 2 m/s S=D÷T =8÷ 2 = 4 m/s

Distance-Time Graphs Constant speed No speed (moving away) (moving closer) (standing still) (and faster!)

Interpreting a D-T Graph (1) Analysis: Distance (m) • The distance (m) stays the same as the time (s) increases Time (s) • Therefore, the object is at rest (not moving)

Interpreting a D-T Graph (2) Analysis: Distance (m) • The object is moving away from the reference point • The object is moving at a constant speed Time (s) • The object is moving quickly

Interpreting a D-T Graph (3) Analysis: Distance (m) • The object is moving towards the reference point • The object is moving at a constant speed Time (s) • The object is moving slowly

Interpreting a D-T Graph (4) Distance (m) Analysis: • In Part A, the object is moving away at a constant speed B A C Time (s) • In Part B, the object is at rest • In Part C, it is moving towards at constant speed

Any Questions?

Motion Part 3: Velocity and Acceleration

Review: Speed is the distance an object travels in a specific amount of time. To calculate speed: Speed = Distance ÷ Time Distance is in meters (m) Time is in seconds (s) Speed is in meters per second (m/s)

Velocity Sometimes, knowing the speed isn’t enough. For example, sailors must know the speed and direction their boat is travelling in. Velocity is a description of both speed and direction. e. g. a sailboat travelling at 20 kph in a SE direction

Velocity Sometimes, knowing the speed isn’t enough. For example, sailors must know the speed and direction their boat is travelling in. Velocity is an example of a vector, a quantity that has both magnitude and direction.

Acceleration Objects can speed up, slow down or change direction. Acceleration measures how much an object’s speed changes over a certain time. Acceleration can be: A change in speed A change in direction A change in speed & direction

Acceleration can be positive, negative or zero. Positive Acceleration Object speeds up Negative Acceleration Object slows down Zero Acceleration Constant or no speed

Acceleration Formula for acceleration: acceleration = change in velocity time a = Vfinal - Vinitial t Velocity: meters per seconds (m/s) Time: seconds (s) Acceleration: meters per second squared (m/s 2)

Example 1 A motorcycle’s velocity at the top of the hill is 11. 0 m/s. 4. 0 seconds later it reaches the bottom of the hill with a velocity of 20. 0 m/s. What is the acceleration of the motorcycle? a = Vfinal - Vinitial t a = 20. 0 m/s - 11. 0 m/s 4. 0 a = 9. 0 m/s 4. 0 a = 2. 25 m/s 2

Example 2 A speed skater just finished a race. After she crossed the finish line, she coasted to a complete stop. If her initial speed was 13. 0 m/s and her acceleration was 2. 9 m/s 2, how long did it take her to stop? a = Vfinal - Vinitial t - 2. 9 m/s 2 = 0. 0 m/s - 13. 0 m/s t t (- 2. 9) = - 13. 0 m/s t = - 13. 0 m/s / - 2. 9 t = 4. 5 s

Any Questions?

Motion Part 4: Speed-Time Graphs

Interpreting a D-T Graph (1) Analysis: Distance (m) • The distance (m) increasing as time (s) passes • The distance gets larger and larger with each second Time (s) • This shows (+) acceleration

Interpreting a D-T Graph (1) Analysis: Distance (m) • The distance (m) decreasing as time (s) passes • The distance gets smaller & smaller with each second Time (s) • This shows (-) acceleration

Interpreting a D-T Graph (3) Analysis: Distance (m) • The distance (m) from a reference point is increasing • It is increasing at a regular rate Time (s) • This shows (0) acceleration

Interpreting a D-T Graph (3) Analysis: Distance (m) • The object is moving towards the reference point • The object is moving at a constant speed Time (s) • The object is moving slowly

Interpreting a S-T Graph (4) Analysis: Speed (m/s) • The speed (m/s) is constant as time (s) passes • The object’s speed is not changing Time (s) • This shows (0) acceleration

Interpreting a S-T Graph (5) Analysis: Speed (m/s) • The speed (m/s) is increasing as time (s) passes • The object speed is changing Time (s) • This shows (+) acceleration

Any Questions?