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Speed, Velocity, Acceleration BY: BRIANNA SHIELDS.

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Presentation on theme: "Speed, Velocity, Acceleration BY: BRIANNA SHIELDS."— Presentation transcript:

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2 Speed, Velocity, Acceleration BY: BRIANNA SHIELDS

3 DO NOW- Get hmwk out!  Complete the physics handout on front counter

4 GOAL  To interpret graphs and solve word problems involving speed, velocity, acceleration and momentum

5  Motion  Change in position during a time period  3 types of motion –Speed –Velocity –Acceleration

6  Speed  1. Definition: Rate at which an object moves  2. Formula: Distance divided by time (d/t)  3. Units: m/s or km/s

7  Speed  4. Constant speed - speed that doesn’t change  5. Average speed- add speeds, divide by total number

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9  Speed  6. Graphs: –Time: x-axis –Distance: y-axis –Constant speed –Changing speed Copy samples of these into your notebook

10 Cheetah 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?

11 Bicycle Graph  After one hour how far had she traveled?  Two hours?  Three hours?  Four hours?  Is she traveling at a constant speed? Why/why not  During which hours was her speed the greatest?  What does the flat line on the graph indicate?

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13 Calculating 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/sec  2: d/t 10 km/ 2800 sec km/sec  Runner 2 has greatest average speed!

14 Calculating 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 239 miles/ 0.75 hr

15  Velocity  1. Definition: Describes speed plus direction (n, s, e, w)  2. Formula: D/T plus direction  3. Units: m/s or km/s, north, south, east or west

16  Velocity  4. Velocities can be combined –Add velocities when in same direction –Velocities in opposite direction= subtract

17  Velocity  5. Graphs: –Time: x-axis –Distance: y-axis –(same as speed graphs but also has direction)

18 Calculating Velocity: Example  If a runner is running east at 10 m/s sec, what is her velocity?  10 m/s east

19 Calculating 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

20 Calculating 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?  15-8  7 km/hr upstream

21 Calculating 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)

22  Accelerati on  1. Definition: Rate of change in velocity –Speeding up, slowing down, changing direction  2. Formula: Final velocity minus original velocity, divided by time  3. Units: m/s/s or km/s/s

23  Accelerati on  4. Increasing velocity - positive acceleration  5. Decreasing velocity - negative acceleration- deceleration

24  Accelerati on  6. Graphs –X- axis- time –Y-axis- distance –Object must be changing velocity –Line, is smooth and curved (not straight)- “changing line”

25 Acceleration Graph- Race Car  1. From 0-1 sec how far did the race car go?  2. From 1-2 sec?  3. From 2-3 sec?  4. Is the car accelerating or decelerating? Explain.

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30 Calculating 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-Vo T m/s/s

31 Calculating 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-Vo T A = = -7.5 m/s/s 2

32 Calculating 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-Vo T A = = 5.0 m/s/s 5

33  Momentu m  1. Definition: Depends on object’s mass and velocity –Related to force upon impact  2. Formula: Mass x velocity  3. Units: Kg.m/s

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37 Calculating 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

38 Calculating 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? Explain  If they have approximately the same mass, the faster car will gather more momentum, according to the equation: momentum = mass x velocity

39 Calculating 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

40 Websites  Fear of Physics Fear of Physics

41 Assignment  Write the homework assignment into your agenda: –Practicing Motion


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