PhysicsBell
• 1)How many seconds are in one year?• 2) How tall are you in inches.• 3) There are 2.54 centimeters in one inch,• How tall are you in centi-meters?• 4) There are 100 centi-meters in one Meter.
How tall are you in meters?
The Drop!!!
The Drop
• Goals:1.Measure the Distance and Time for an object
to fall to the floor from a given height.2.Design a scientific experiment
Still falling
1. Choose a challenge2. Create a data table3. Perform the experiment4. Make observations and questions5. Answer Analysis Questions
Bell Quiz
1) One Billion has ______ zeros.
2) One Billion is 1 x 10?
3) (5 x 103 ) + (5 x 103 ) = ( ? x 103 )
4)(5 x 103 ) - (4 x 103 ) = ? X 10?
Dropped!
• Goal:• Complete the activity and analysis• Peer Review!!!! See Rubric.
Bell
• A car travels 10 meters in 5 seconds, how fast is it going?
• A car begins from rest and goes 500 meters in 25 seconds. What is the average speed?
• In the example above, how fast will the car be going after 25 seconds, assuming that is speeds up at a constant rate?
• Whatis the acceleration?
Unit 2 notes
Motion in one directionLinear Motion
Rate
• A quantity divided by a time• Examples…
Speed
• Total distance divided by total time• Speed = Change in Distance/time
• Ex. 36 feet in 10 sec. • Is 3.6 ft/sec
Reference Frames and Displacement
Change in Position, regardless of distance traveled.
The displacement is written:
Displacement is positive.
Displacement is negative.
Velocity
• SI units. Meters for distance and sec for time• Units for velocity are m/s• Velocity is change of displacement in time• V = Δx/t• Velocity is DIRECTION and SPEED• Instantaneous vs. Average
2-2 Average Velocity
Speed: how far an object travels in a given time interval
Velocity includes directional information:
(2-1)
Graphical Analysis of Linear Motion
The displacement, x, is the area beneath the v vs. t curve.
acceleration
• Rate of change of velocity, velocity divided by time.
• A = change in velocity in time • Acceleration = Δv/t• SI units are meters per second per second or m/s2
• Other units miles per hour per second• Kilometers per hour per secondEx.
2-4 AccelerationAcceleration is the rate of change of velocity.
Uniform AccelerationNAME Symbol Units (measurement)
Displacement Δx Meters
Velocity V Meters / second
Change in Velocity ΔV Meters / second
AccelerationTime
a t
Meters / (second)2
seconds
Average Velocity V = Δx / time
Acceleration a = ΔV / time
Distance Δ x = Vit + ½ a t2
The Bee and the Bicycle• Two bicycle riders approach each other from
20 km away, each with a speed of 10 km/hour. When they are 20 km apart, a FAST bumble bee flies back and forth between them at 30 km/hour.– Draw a picture– How long will it take the bicycles to pass each
other?– How far (total distance) will the bee travel before
the bikes meet?– How fast is the Bee moving relative to the bike
that is chasing it?
Bell 8/281. You can run 4.0 Km in 30 minutes. What is
your average speed in Km/hour?2. A car begins at rest and accelerates at 5 m/s
for 12 seconds. How fast will it be going?3. How far will the car have gone after 5
seconds?4. A car begins at x = 15meters and moves
backward 10 meters. What is the displacement and final position?
Free fall
Free fall
How was this picture taken?
Free Fall
• Acceleration due to gravity is ‘g’• ‘g’ is 9.8 m/s per sec, or 10 m/s2
• If…. No air resistance• If…. At the surface of the earth
• `
Free Fall:
• How Fast?
• What is g?
• V = gt• How fast is something going after 1,2,3,4 sec?• What about something thrown straight up at
50 m/s?
Why do objects of different masses fall with the same acceleration?
Velocity vs. time graph
Bell: 8/29/13
• A ball is dropped from a balcony. 1.How fast will it be going after 1, 2, 3, 4
seconds?2.Just before it hits the ground, it is going
58m/s. How much time did it take to fall?3.You want to toss the ball back up to the
balcony. How fast do you need to throw the ball upward (minimum speed?)
Free Fall
• How Far?• ∆x = ½ (a)(t)2
• a = g = 10m/s/s
• d = 5 t2
• How far has an object fallen after 1,2,3,4 sec?• What about an object that is thrown up at 50
m/s, how high will it go?
Displacement = 5t2
Graphing Motion1. The slope of a distance vs. time graph IS the
VELOCITY during that time intervalV = x/t
2. The slope of a velocity vs. time graph IS the acceleration
A = v/t
3. Distance = velocity x time, so the AREA under a velocity vs. time graph IS the DISPLACEMENT!x = vt
Sketch the distance vs time graph and velocity vs. time graph for each situation.
A. An object at restB. An object moving in the positive direction
with a constant speedC. An object moving in the negative direction
with a constant speedD. An object that is accelerating in the positive
direction, starting from rest
Reaction Time
• How far does an object fall in one second?• How far does an object fall in ½ second?• If an object falls 7 cm. How long will it be
falling for.
Graph Matching Analysis: P 2
1. What is the significance of the SLOPE of a distance vs time graph?
2. What type of motion is occurring when the slope of a distance vs. time graph is zero?
3. What type of motion is occurring when the slope of a distance vs. time graph is constant?
4. What type of motion is occurring when the slope of a distance vs. time graph is changing?
Part 3
1. What is the significance of the slope of a velocity vs. time graph?
2. What type of motion is occurring when the slope of a velocity vs. time graph is zero?
3. What type of motion is occurring when the slope of a velocity vs. time graph is not zero?
