What is motion? Acceleration Momentum Motion and Momentum What is motion? Acceleration Momentum

What is Motion? Changing Position All matter in universe is constantly in motion If something is changing position it is in motion To determine if an object is in motion, a point of reference is needed

Distance and Displacement Final position of motion depends on both distance traveled and the direction Distance would be the actual movement from start to end Displacement includes the distance between start and finish and the ending point…. Sometimes it will be equal to zero, if you end up at same point that you started See example on page 523

Speed Speed is the distance an object travels in a period of time S = D/T (units would be meters/second) Average speed is found by taking total distance traveled by the total time Instantaneous speed is the speed of an object at one instant of time (police using radar is an example) Constant speed is speed that doesn’t vary on its movement (cruise control on car is put on constant speed)

Graphing Motion Graphing using time (x axis) and distance (y axis) Constant speed

Graphing Motion Which I moving at a faster pace?

Velocity Velocity of an object is the speed of an object and the direction of its motion The difference of velocity and speed is that velocity refers to a direction Velocity changes if you change speed or if you change direction V = D/T (any changes in speed or direction changes its velocity) Units are in m/s

Acceleration Acceleration is the change of velocity divided by the time it takes for the change to occur Acceleration has direction because it refers to velocity, so a change of direction also changes its acceleration A = Vf – Vi (units are in m/s/s) (or m/s2) t

Acceleration Speeding up: a positive acceleration results in an object speeding up Slowing down: a negative acceleration results in an object slowing down also known as deceleration Changing Direction: Any change of direction results in change of velocity and a change in acceleration

Acceleration Page 531 To solve physic problems these steps need to be shown on your paper 1. list all information given 2. write down what your ask to solve 3. write down formula that you are using 4. plug in data into formula including units 5. solve and check if the answer makes sense 6. record answer with its proper units

Acceleration Bike increases speed from 4 m/s to 6 m/s in 5 seconds Vi = 4 m/s A= 6m/s – 4 m/s Vf = 6 m/s 5 s T = 5 s A = ? A = .4 m/s/s or .4 m/s2 A= Vf-V bike speeds up .4 m/s every second T

Acceleration Bike slows down from 4 m/s to 2 m/s in 5 seconds Vf = 2 m/s A = 2 m/s- 4m/s Vi = 4 m/s 5s T = 5 s A=? A = -.4 m/s/s or -.4 m/s2 A = Vf-Vi (notice it is a negative acceleration) T

Acceleration Graphing accelerated Motion

Graphing accelerated motion http://www.physicsclassroom.com/mmedia/i ndex.cfm#kinema

Collisions When a collision occurs changes in motion of the colliding objects depends on their masses and their velocities before the collisions Mass: is the amount of matter in an object (the more mass, the harder to change its motion) The tendency of an object to resist a change in its motion is called inertia and is dependent on its mass

Momentum A larger mass or an object moving faster is harder to stop than a smaller one or a slower one Momentum is a measure of how hard it is to stop an object and is dependent on the objects mass and velocity P = mv (where P is momentum, m is mass and v is velocitiy)

Momentum Use the same process as before To solve physic problems these steps need to be shown on your paper 1. list all information given 2. write down what your ask to solve 3. write down formula that you are using 4. plug in data into formula including units 5. solve and check if the answer makes sense 6. record answer with its proper units

Solving page 534 Calculate momentum of a 14 kg bike traveling 2m/s M=14 kg p = mv V= 2m/s P =? P = 14 kg X 2 m/s p = 28 kg*m/s

Conservation of Momentum The total momentum of a group of objects remains constant unless outside forces act on the group is known as the law of conservation of momentum In a cue ball hitting billiard balls all the momentum of the original collision equals all of the momentums of the billiard balls when they are hit excluding outside force like friction

Types of collisions Some collisions bounce off each other, others stick together after contact

Using momentum conservation Momentum before equals momentum after collisions p =p M1V1 =M2V2

Using momentum conservation Page 536 backpack weighs 2 kg is thrown at velocity of 5 m/s east. A student grabs it that weighs 48 kg. What was his velocity after catching it Mbp = 2 kg Mbp(Vbp) = (Ms + Mbp)(Vs) Vbp = 5 m/s 2kg*5m/s=(2 kg+48kg)*Vs Ms = 48 kg 10kg*m/s=50kg*V2 Vs = ? .2 m/s east = Vs

Colliding and bouncing off 2 objects same mass and same speed collide Since they have same momentum before collision, they have zero momentum After collision the 2 objects bounce off with same velocity but opposite directions, therefore there is no momentum after collision