How do we know if something is moving quickly or slowly? What about the speed of things we can t see? (think about internet speed ) Has our idea of

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2 How do we know if something is moving quickly or slowly? What about the speed of things we can t see? (think about internet speed ) Has our idea of speed changed over time?

3 8.6B SS - differentiate between speed, velocity, and acceleration

4 When it comes to movement, human beings are fascinated by speed. From vintage muscle cars to turbo-powered sports cars, we love things that go fast. We even have track and field competitions and the Olympic Games that celebrate those humans that can move most quickly.

5 Let s talk about how we view speed and how we decide if something is fast

6 Usain Bolt blitzed the field once again in the 100m sprint at the Rio Olympics, making it three gold medals in a row in the event. So how fast can he run? And how does that top speed compare?

7 Bolt in the 2016 Rio Olympics

8 Bolt's winning time of 9.81 secs equates to an average speed of 36.7 kmh. However, that's just an average - his actual top speed is much faster than that. In 2009 when he set a new world record of 9.58sec, it was calculated that Bolt's speed peaked at meters per second or kmh. (1 km =.6miles) he ran 27.3 mph!

9 Video on Katie

10 Lindsey Vonn best downhill skier

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12 If you want to be the fastest in the world you have to understand some basic (and not so basic) physics! Let s start by adding to our understanding of how things move

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14 Is a way to describe motion. Average speed - Rate of motion calculated by dividing the distance traveled by the amount of time it takes to travel that distance Constant speed - Speed that does not change Instantaneous speed - Speed of an object at any given time Units: Measured in m/s (the given distance/time)

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16 Speed is calculated by dividing distance by time. Remember average speed is speed over a given amount of time! So the formula is:

17 A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running?

18 A football field is about 100 m long. If it takes a person 20 seconds to run its length, how fast was the football player running? Speed = Distance Time Speed = 100 m 20 s Speed = 5m/s Remember to include the UNITS!!

19 Velocity is speed with direction. Calculating velocity is the same as calculating average speed (distance/time). The difference is that velocity is what physicists call a vector. A vector means size and direction. There must be direction. For example: Speed = 3 m/s Velocity = 3 m/s, heading northeast Velocity = Final Distance Initial Distance Final Time Initial Time

20 The 3 vehicles shown are all traveling at a speed of 15 m/s, but only the pick up truck has a changing velocity (and acceleration but we will get to that)

21 Speed describes distance and time Velocity describes distance, time, and direction You can say the top speed of an airplane is 300 kilometers per hour (kph). But its velocity is 300 kph in a northeast direction.

22 SPEED Speed is considered one dimensional in physics speed is a scalar quantity What this means is that speed has only one number associated with it VELOCITY A vector is a quantity that has both magnitude (numerical size) and direction. A simple example is velocity. It has a magnitude, called speed, as well as a direction, like North or Southwest or 10 degrees west of North.

23 Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity. If an object is not changing its velocity, then the object is not accelerating.

24 Acceleration does NOT = going faster! Acceleration is a change in direction and/or speed, not just limited to speeding up (which is how most people misuse the term). It can also mean to slow down or change direction. It sounds strange to us, but physicists will say when the car is slowing down at a stop sign that it is accelerating!

25 Acceleration is a change in velocity by Changing speed a change in speed could be: 1. Starting 2. Stopping 3. Speeding up 4. Slowing down Acceleration also happens when - changing direction

26 Acceleration can be positive or negative Speeding Up Positive acceleration (+) Slowing Down Negative acceleration (-) Units measured in m/s 2 Notice how similar this is to speed units! Acceleration is caused by unbalanced forces Calculating Acceleration: Remember what the triangle is?

27 How are they connected? Acceleration is a change in speed, direction or BOTH of these at the same time! Again, acceleration is simply the measure of the change in velocity. It occurs when there is a change in speed, direction, or both.

28 If you kick a soccer ball down the field during a game, the direction of the ball and the speed at which it travels is constantly changing. This means that the acceleration of the ball is continuous as well.

29 Which of the following sentences contain an example of velocity and which contain an example of speed? A. Five seconds into the launch, the rocket was shooting upward at 5000 meters per second. B. Cheetahs can run at 70 miles per hour. C. Moving at five kilometers per hour, it will take us eight hours to get to the base camp. D. The car covered 500 kilometers in the first 10 hours of its northward journey. Velocity Speed Velocity Speed E. Roger Bannister was the first person to run one mile in less than four minutes. Speed

30 Now that you have filled in the blanks with either speed or velocity. Go back to the sentences that are examples of velocity. Highlight or underline the key words that make them examples of velocity. Hint: look for directional words!

31 What do you remember about the types and forms of energy? There are two types of energy - potential and kinetic. Under these two types are forms that energy can be found Find the handout that talks about the types and forms. Read over it now and fill in the missing information on your notes page.

32 Coaster animation

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35 The car s PE is greatest at the highest point, due to gravitational potential energy. The kinetic energy will be highest at the bottom of the first hill, where is moving the fastest (or has the most speed)

36 As the car travels through the rest of the roller coaster, friction and air resistance will slow the car Each hill after the first one has to be lower because the energy is lost (converts to thermal energy)

37 As the bicyclist starts up the hill, think about the types of energy that will occur. At the top of the hill, what type of energy is most prevalent? At the bottom of the hill?

38 When the rider is at the top of the hill, her potential energy is the greatest and her kinetic energy is the least. Kinetic energy is greatest at the bottom of the hill (her speed is higher)

39 So how do these two relate to each other? Well, kinetic energy is movement. Whenever stored energy begins (PE) to move, it coverts to kinetic energy. So kinetic energy is motion and when something is in motion, we can measure how far it travels in a certain amount of time in other words SPEED!

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41 Brain Pop Crash Course