Motion

 a change in position, or location of a place or object, over a certain amount of time  relies on a frame of reference or something assumed to be stationaryframe of reference  is relative to a frame of reference i.e. – you may be stationary as you sit in your seat, but you are moving 30 km/sec (≈19 mi/sec) relative to the Sun Relative Motion Simulation

Frame of Reference (Reference Point)  a stationary location or object to which you compare other locations or objects  none are truly stationary relative to all others – what is not moving in one is moving in another  Task Using your body as the frame of reference, provide your classmate with directions to the classroom door. How does your frame of reference impact the directions you give others? How does frame of reference explain why people thought the Earth was in the center of all celestial bodies?

Speed  the rate at which an object moves  a measure of how fast something moves, or the distance it moves, in a given amount of time  Formula:  typically expressed in units of m/s  is considered average when taking into account the total distance covered and the total time of travel  is considered constant when it does not change  is considered instantaneous when it represents a specific instant in time S = d t 6 meters 00: What is the ball’s speed?

Interesting Speeds meters/secondmiles/hour Cockroach Kangaroo 1534 Cheetah 2760 Sound (in 20 0 C air) Space Shuttle (getting into orbit) 7,82317,500 Light 300,000,000671,080,888

Practice Problems - Speed 1.If you walk for 1.5 hours and travel 7.5 km, what is your average speed? 2. Calculate the speed of a bee that flies 22 meters in 2 seconds. S = d t S = d t S = = 7.5 km 1.5 hr 5 km hr S = 22 m 2 sec = 11 m sec

The Speed Triangle. S S = d t t t = d S d d = S t. S t d

Distance-Time Graph Shows how speed relates to distance and time Time (seconds) Distance (meters) A B C This distance-time graph will show a student’s speed as he returns to class after lunch. What is the speed from 0-A ? What is the speed from A-B ? What is the speed from B-C ? What is the student’s average speed?

Can you figure this out? Two birds perched directly next to each other, leave the same tree at the same time. They both fly at 10 km/h for one hour, 15 km/h for 30 minutes, and 5 km/h for one hour. Why don’t they end up at the same destination?

Velocity  the rate of change of an object’s position  speed in a given direction  is considered constant when speed and direction do not change  changes as speed or direction changes  is a vectorvector  can be combined (added if moving in the same direction and subtracted if moving in the opposite direction) i.e. – If you are walking at a rate of 1.5 m/s up the aisle of an airplane that is traveling north at a rate of 246 m/s, your velocity would actually be m/s visuals taken from: 29 m/s east 25 m/s west

Acceleration  the rate at which velocity changes  occurs when something is speeding up (+), slowing down (-), or changing direction  Formula:  typically expressed in units of m/s 2  is always changing, and considered centripetal, when traveling in a circle a = v f – v i t Explain how both cars are accelerating.

Practice Problems - Acceleration 1.Tina starts riding her bike down a hill with a velocity of 2 m/s. After six seconds, her velocity is 14 m/s. What is Tina’s acceleration? 2. A motorcyclist goes from 35 m/s to 20 m/s in five seconds. What was his acceleration? a = = 14 m/s - 6 s 2 m s 2 a = 20 m/s - 5 s = -3 m s 2 a = v f – v i t a = v f – v i t 2m/s 35 m/s

Velocity-Time Graph Shows how acceleration relates to velocity and time Time (seconds) Velocity (meters/second) This velocity-time graph will show a student’s acceleration as she returns to class after lunch. Describe the student’s acceleration as she travels to class?

Momentum  a measure of mass in motion  the product of an object’s mass and velocity  Formula:  typically expressed in units of kg·m/s  is in the same direction as the velocity  makes an object harder to stop or change direction as it increases  is a vector  can be transferred  is conserved p = mv 20 kg Which object has more momentum – the curling rock or the hockey puck? Explain your reasoning kg Describe the scenario where the puck would have more momentum than the curling rock?

Practice Problems - Momentum 1.What is the momentum of a 7.3 kg bowling ball moving at 8.9 m/s? 2. At a velocity of 8.5 m/s, Tim moves down a hill on an inner tube. If his mass is 59 kg, how much momentum does he have? p = mv p = = (7.3 kg)(8.9 m/s)65 kg · m/s p = (59 kg)(8.5 m/s) = 502 kg · m/s

Vector  a quantity that has both direction and magnitude (size)  drawn as an arrow which shows direction and magnitude (length of arrow) consists of two parts: tail and head Tail Head Consider the vectors above. Describe the direction and relative magnitude (speed) of each car based on the vector.