Motion All motion is relative Name some types of motion Cars, people, stars, earth, atoms, electrons How do we describe motion? As a rate That is some quantity over time Ex. d/t and v/t Why is motion relative? We need a frame of reference Something to compare our motion with.

Speed Describe speed? d /t What are some units for speed? mi/h, km/h, m/s

What is the difference between average speed and instantaneous speed? Average is a total distance over a total time or an average of all of the speeds during a time interval. Instantaneous speed is the speed at a particular time. Which does your car speedometer show? Instantaneous

Average speed example If you traveled this summer to Florida you might have traveled a distance of 1200 miles. If you covered that distance in 16 hours, what was your speed? Is this answer an average speed or an instantaneous speed? Average

What is the difference between speed and velocity? Velocity has direction

Describe constant speed. Traveling at the same rate d / t What are the parts of your car that change speed? Gas, brakes

Describe constant velocity. Traveling with constant speed and constant direction. What are the parts of your car that change velocity? gas, brakes and the steering wheel

Vectors vs. Scalars What is a vector? Something that has magnitude and direction What are some examples of vectors? Velocity, displacement, acceleration, force What is a scalar? Something that has magnitude only What are some examples of scalars Speed, distance, time, volume

Is it possible to have a constant speed and be changing velocity? Yes, by changing direction.

What do we call it when we change velocity? Acceleration a = v/ t What does the  mean? Change a = vf – vi / t

Acceleration examples A car increases velocity from 0 to 60 mi/h in 4.8 s. What is it’s acceleration? A car changes it’s velocity from 60 mi/h to 0 mi/h in 1.8 s. What is it’s acceleration?

Motion graph d/t not moving What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs v/t not moving What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs a/t not moving What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs d/t constant velocity What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs v/t constant velocity What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs a/t constant velocity What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs d/t constant acceleration What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs v/t constant acceleration What does the slope of the line represent? What is the numerical value of the slope?

Motion graphs a/t constant acceleration What does the slope of the line represent? What is the numerical value of the slope?

What is free fall? Something falling through the air as a result of gravity. How fast does it fall? -9.8 m/s2 What does the negative sign tell you? Direction

How long was it in the air? Make a list of everything you might be asked about something in free fall. How fast is it falling? Initial and final? How far did it fall? How long was it in the air? What variables are represented in the above questions? a, vf, vi, d, t

How fast meaning acceleration? Gravity = -9.8 m/s2 What is the formula for acceleration? vf = vi + at

How fast meaning final velocity? vf = vi + at What type of velocity is this, average or instantaneous?

If you drop a ball from rest what is it’s velocity 1s later? vi = 0 m/s vf = ? a = -9.8 m/s2 Show your work

Make a data table Time (s) vf (m/s) 1 10 2 20 3 30 6 60

How far? At the end of 1 second the instantaneous speed is 10 m/s Does this mean it fell 10 m in the first second? NO It did not average 10 m/s for the whole first second. The velocity at the end of the first second was 10 m/s. We need to know the average speed during the first second in order to find out how far it fell.

How could you find the average speed between 0 and 10 m/s? Mathematically how do you find an average? Add up the numbers and divide by how many you have. (vi + vf) / 2 Therefore (0 + 10 m/s) / 2 = 5m/s So the ball averaged 5 m/s during the first second and fell 5 m

Displacement formula To find displacement we use these two formulas v = d/t v = (vf + vi) / 2 d = v * t d = [(vf + vi)/2]t d = ½ (vf + vi)t

Displacement formula pre-ap What does the area of the green box represent? vf v * t = d displacement vi How do you find the area for the red section? ½ base * height or ½ t(vf-vi)

Displacement formula pre-ap What is the area of the green and red sections? vf = vi + at at = (vf – vi) d = vit + ½ t(vf - vi) vf vi d = vit + ½ at2

Displacement formula What if we didn’t know vf and we still wanted to know displacement? d = ½ (vf + vi)t vf = vi + at d = ½ [(vi + at) + vi]t d = vit + ½at2

Displacement formula What if we didn’t know time and we still wanted to know displacement? vf = vi + at d = vit + ½at2 t = vf –vi / a d = vi[(vf-vi)/a] + ½ a[(vf-vi)/a]2 vf2 = vi2 + 2ad

Big box of formulas vf = vi + at d = ½ (vf + vi)t d = vit + ½at2 vf2 = vi2 + 2ad

Problem solving strategy Make a list of information from the problem Add to the list what you are looking for We always know vi Pick an equation based on what is not in your list Solve the equation for the variable in question