• Over what interval(s) on the graph above is the object speeding up?

• Over what interval(s) on the graph above is the object slowing down?

• At what point(s) on the graph above is the object changing direction?

• Over what interval(s) does the object appear to be traveling at a constant speed?

• When is the object traveling backwards?

UM.6

Describe the motion and draw a position vs. time graph

• Cart rolling down a ramp (sensor at bottom of ramp)

• Ball being thrown up

Now draw the motion map for each

Now draw the velocity vs. time graph for each

Describe the motion, draw a position vs. time graph, and a motion map for each section of the

graph• A to B• B to C• C to D• D to E• E to F• F to G

v (m/s)

t (s)5

A

B

What is the difference between average velocity and instantaneous velocity?Draw this graph in your notes.

1. Describe the motion of each object.

2. Is there any place where A has a greater speed than B? If so, where?

3. Is there any place where A has a speed equal to B? If so, where?

4. Is there any place where A has a slower speed than B? If so, where?

1. Relative to the car what is the velocity of the runner?2. Relative to the balloon what is the velocity of the car?3. Relative to the boat what is the velocity of the hitch hiker?4. Relative to the runner what is the velocity of the river?

All velocities are relative to the Earth.

Concept Check N1.1

Concept Check N1.6

When the pellet fired into the spiral tube emerges, which path will it follow? (Neglect gravity). Explain thoroughly using physics!

Concept Check N1.3, N1.5Which of these pictures represent a zero net force (balanced forces) situation? Use physics to justify your answers.

A

B

C

D E F

G

H

Concept Check for AccelerationUA.1

• Definition:• Equation: • Units :• To cause an acceleration on an object there

must be . . .• What do we know about F in an object that

is changing its velocity?• What are the three different forms of

acceleration?

Rate of change in velocity∆v / t or v f - vo / t

Meters/sec/sec or m/s2

an outside force

F is not zero

Speeding up, slowing down, or changing direction

Lab Concept Check UA.7, N2.1

Relationship between force and acceleration

• What is the independent variable? How are you changing it?

• What is the dependent variable? How are you measuring it?

• What needs to be held constant throughout the experiment?

Relationship between mass and acceleration

• What is the independent variable? How are you changing it?

• What is the dependent variable? How are you measuring it?

• What needs to be held constant throughout the experiment?

Concept Check UA.3, UA.4, N2.2, N2.5

• Three people are pulling on a wagon applying forces of 100 N,150 N, and 200 N.

• The wagon has a mass of 25 kilograms.• Determine the acceleration and the direction the wagon

moves.

Concept Check N2.9• An airplane needs to

accelerate at 5 m/sec2 to reach take-off speed before reaching the end of the runway.

• The mass of the airplane is 5,000 kilograms.

• How much force is needed from the engine?

Concept Check N2.9• A tennis ball contacts the racquet for much less than one

second. • High-speed photographs show that the speed of the ball

changes from -30 to +30 m/sec in 0.006 seconds. • If the mass of the ball is 0.2 kg, how much force is applied

by the racquet?

Concept Check: Falling with air resistance N2.7

t = 0 sec

t = 1 sec

t = 2 sec

2 balls of same size but different masses are let go at the same time – both start with an acceleration of -9.8 m/s/s

2 balls both receive same amount of air resistance because they are the same size. Acceleration has decreased for both because net force has decreased

Ball on the left has reached terminal velocity because the net force is zero so the acceleration is zero. Ball on the right is still speeding up because it does not yet have a net force of zero so the acceleration is not zero.

Concept Check N2.7Which encounters the greater force of air resistance

—a falling elephant or a falling feather?

Concept Check N2.7Two smooth balls exactly the same size, one made of wood and the other made of iron, are dropped from a high building to the ground below. The ball to encounter the greatest force of air resistance on the way down is the:

a) wooden ballb) iron ballc) ... both the same

Concept Check N2.7As she falls faster and faster through the air, her acceleration (change in velocity)

a) increasesb) decreasesc) remains the same

Concept Check N2.7What will be the acceleration (change in velocity) of a rock thrown straight upward at the moment it reaches the tippity-top of its trajectory (no air)?

Concept CheckIdentify Newton’s 3rd law in each of these situations:

Concept Check

Rockets are unable to accelerate in space because ...a. there is no air in space for the rockets to push off of. b. there is no gravity in space.c. there is no air resistance in space.d. ... nonsense! Rockets do accelerate in space.

Concept CheckWhile driving down the road, an

unfortunate bug strikes the windshield of a bus. Quite obviously, this is

a case of Newton's third law of motion. The bug hit the bus and the bus hit the bug. Which of the two forces is greater: the force on the bug or the force on the

bus?

In the tug-of-war, what is the reading on the scale?

A. 0 NB. 1000 NC. 2000 ND. 3000 N

1000 N 1000 N0

3000

2000

1000

What will the scale read that is pulled from both sides by 10 N weights?

A. 0 NB. 10 NC. 20 ND. 30 N

How would you rescue an ice skater that fell through the ice?

Concept Check P.1

What would happen if a bag of chips sealed at sea level were

taken to the top of a mountain?

Concept Check P.2

Concept Check P.2

Watch the demonstration up front and then explain in detail (using physics) how it works.

Concept Check P.2

Watch the demonstration up front and then explain in detail (using physics) how it works.

Concept Check P.4

• Compare the buoyant force on the two balls.

Concept Check P.5

• Watch the video clips and then apply a physics concept we have learned to each situation.