8Speed 6. Graphs: Time: x-axis Distance: y-axis Constant speed Changing speedCopy samples of these into your notebook
9Cheetah Speed Graph In one second how far had the cheetah run? In three seconds how far had the cheetah run?What was the cheetah’s average speed?
10Bicycle Graph After one hour how far had she traveled? Two hours? Three hours?Four hours?Is she traveling at a constant speed? Why/why notDuring which hours was her speed the greatest?What does the flat line on the graph indicate?
12Calculating Speed: Example If 2 runners ran the same distance (10km) but one completed it in 3600 seconds and the other in 2800 seconds, what were each of their average speeds?1: d/t 10km/3600 sec km/sec2: d/t 10 km/ 2800 sec km/secRunner 2 has greatest average speed!
13Calculating Speed: Example Spirit of Australia, a hydroplane boat, made speed records by traveling 239 miles in 0.75 hours (45 minutes). What is it’s record breaking speed?d/t miles/ 0.75 hr
14Velocity1. Definition: Describes speed plus direction (n, s, e, w)2. Formula: D/T plus direction3. Units: m/s or km/s, north, south, east or west
154. Velocities can be combined Velocity4. Velocities can be combinedAdd velocities when in same directionVelocities in opposite direction= subtract
16Velocity 5. Graphs: Time: x-axis Distance: y-axis (same as speed graphs but also has direction)
17Calculating Velocity: Example If a runner is running east at 10 m/s sec, what is her velocity?10 m/s east
18Calculating Velocity: Example If you’re rowing a boat downstream at 16 km/hr, and the curren is moving at 10 km/hr. How fast does the boat “look” like it’s going to someone on shore? (Draw a picture too!)26 km/hr downstream
19Calculating Velocity: Example If you’re rowing a boat upstream at 15 km/hr, against a current moving at 8 km/hr. What is you’re actual velocity to an observer on the shore?15-87 km/hr upstream
20Calculating Velocity: Example If you are running up an escalator at 2 steps per second and its moving downward at 3 steps per second, what is the total velocity? In what way are you moving?3-2-1 (you are actually moving backwards, down the escalator, although you’re running up it)
211. Definition: Rate of change in velocity Acceleration1. Definition: Rate of change in velocitySpeeding up, slowing down, changing direction2. Formula: Final velocity minus original velocity, divided by time3. Units: m/s/s or km/s/s
29Calculating Acceleration: Example A roller coaster’s velocity at the top of a hill is 10m/s. Two sec later it reaches the bottom of the hill with a velocity of 26 m/s. What is the acceleration of the roller coaster?Vf-VoT26-1028 m/s/s
30Calculating Acceleration: Example A roller coaster’s velocity at the bottom of a hill is 25 m/s. Three seconds later it reaches the top of the next hill, moving at 10 m/s. What is the deceleration of the roller coaster?A = Vf-VoTA = = m/s/s2
31Calculating Acceleration: Example A car is traveling at 60 km/hr. It accelerates to 85 km/hr in 5 seconds. What is the acceleration of the car?A = Vf-VoTA = = 5.0 m/s/s5
321. Definition: Depends on object’s mass and velocity Momentum1. Definition: Depends on object’s mass and velocityRelated to force upon impact2. Formula: Mass x velocity3. Units: Kg.m/s
36Calculating Momentum: Examples If 2 football players are running at the same velocity towards an opponent. Player 1 weighed 170 lbs, player 2 weighed 250 lbs. Who is going to move the opponent farther? Why?Since both players were traveling at the same velocity, the larger player will have more momentum, thus, moving the opponent farther
37Calculating Momentum: Examples Why would it be harder to stop a car traveling at 65 miles/ hr than it is to stop one traveling at 35 miles/hr? ExplainIf they have approximately the same mass, the faster car will gather more momentum, according to the equation: momentum = mass x velocity
38Calculating Momentum: Examples What is the momentum of a 0.3 kg bluejay running into a window while flying at 17 m/s?momentum = mass x velocity= 0.3 x 17 = 5.1 kg m/s