mastering physics- kinematics lab

4/7/13 Lab3(kinematics)

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Lab3(kinematics)

Due: 12:39pm on Saturday, February 2, 2013

Note: To understand how points are awarded, read your instructor's Grading Policy.

Video Tutor: Balls Take High and Low Tracks

First, launch the video below. You will be asked to use your knowledge of physics to predict the outcome of anexperiment. Then, close the video window and answer the questions at right. You can watch the video again atany point.

Part A

Consider the video demonstration that you just watched. Which of the following changes could potentiallyallow the ball on the straight inclined (yellow) track to win? Ignore air resistance.

Select all that apply.

Hint 1. How to approach the problem

Answers A and B involve changing the steepness of part or all of the track. Answers C and Dinvolve changing the mass of the balls. So, first you should decide which of those factors, if either,can change how fast the ball gets to the end of the track.

ANSWER:

PHY110ASPRING2013

Lab3(kinematics) Resources

A. Increase the tilt of the yellow track.

B. Make the downhill and uphill inclines on the red track less steep, while keeping the totaldistance traveled by the ball the same.

C. Increase the mass of the ball on the yellow track.

D. Decrease the mass of the ball on the red track.

Signed in as Ellie Kamens Help Close



Correct

If the yellow track were tilted steeply enough, its ball could win. How might you go about calculatingthe necessary change in tilt?

Interactive Figure: Acceleration on an Inclined Plane

Launch and then explore the Interactive Figure below to help you with the following set of questions. Click“Play” and see what happens on the graph and on the dial as the ball rolls down the plane. If you need more

help, click on “How To Use” for more information.

Part A

Click “Play” and see what happens on the graph and on the dial as the ball rolls down the plane. How canyou use the graph of velocity versus time to estimate the acceleration of the ball?

Hint 1. The definition of acceleration.

The acceleration is the time rate of change of velocity.

ANSWER:

Correct

Part B

by estimating the value of the area under the graph

by estimating the value from the vertical axis of the graph

by estimating the value of the slope of the graph

by estimating the value from the horizontal axis of the graph



Try changing the “Angle of Incline.” Then click “Play” to see how the change affects the graph and the dial.How does the acceleration of the ball change as the angle of the inclined plane increases?

Hint 1. The relationship between speed and inclination.

When the plane is steeper, does the ball speed up at a faster or slower rate?

ANSWER:

Correct

Part C

Try changing the “Angle of Incline.” Then click “Play” to see how the change affects the graph and the dial.As the angle of the inclined plane increases, how does the final speed attained by the ball at the bottom ofthe inclined plane change?

Hint 1. The relationship between speed and acceleration.

If the speed of the ball increases at a faster rate along a steeper incline, will the ball be going fasteror slower after the same amount of time?

ANSWER:

Correct

Part D

Try changing the “Angle of Incline.” Then click “Play” to see how the change affects the graph and the dial.Why does the final speed attained by the ball at the bottom of the inclined plane change in the way that itdoes when the angle of the incline plane increases?

Hint 1. The relationship between steepness and inclination.

When you increase the angle of the inclined plane, how does the acceleration of the ball change?Given this result, if the ball is moving for the same duration of time, how will the final speed attained

It decreases.

It stays the same.

It increases.

It decreases.

It stays the same.

It increases.



by the ball change?

ANSWER:

Correct

Part E

How does the distance traveled by the ball in the first half second compare with the distance traveled bythe ball in the second half second?

Hint 1. The relationship between speed and time of travel.

Does the ball move at a faster or a slower speed in the second half second of its travel than in thefirst half second?

ANSWER:

Correct

Part F

Why does the distance traveled by the ball in each half second after it is released change in the way that itdoes?

Hint 1. The relationship between speed and time of travel.

Does the ball move at a faster or a slower speed in the second half second of its travel than in thefirst half second?

ANSWER:

The ball accelerates at the same rate for a longer duration of time.

The ball travels a greater distance in the same duration of time.

The ball accelerates at a greater rate for the same duration of time.

It stays the same.

It decreases.

It increases.



Correct

Interactive Figure: Free Fall Motion with an Initial Velocity

Launch and then explore the Interactive Figure below to help you with the following set of questions. If you need

more help, click on “How To Use” for more information.

Part A

Use the “Initial velocity” slider to set the initial velocity of the launch, and then click “Play.” How does themaximum height achieved by a ball change when the initial velocity at which it is thrown upward isincreased?

Hint 1. The relationship between initial velocity and time to stop.

When you throw the ball up at a greater velocity, does it travel a greater or a lesser distance beforeit begins to turn back toward the ground?

ANSWER:

Correct

The incline plane pushes up on the ball, so it accelerates down at a steady rate.

Gravity is pulling down on the ball, so it moves down at a steady speed.

Gravity is pulling down on the ball, so it accelerates down at a steady rate.

It stays the same.

It decreases.

It increases.



Part B

After the ball is thrown upward, it eventually turns back downward, passing through the zero line (thehorizontal axis on the graph). How does the time the ball takes to return to the zero level change when theinitial velocity of the ball is increased?

Hint 1. The relationship between distance traveled and time.

When you throw the ball up higher, will it take a longer or shorter time before the pull of gravitymakes it turn back toward the ground?

ANSWER:

Correct

Part C

How does the velocity of the ball at the maximum height change when the initial velocity at which it isthrown upward is increased?

Hint 1. Motion of ball at the top.

At the maximum height, is the ball moving upward or downward? If neither, describe what the ball isdoing.

ANSWER:

Correct

Part D

What is the value of the velocity of the ball when it reaches its maximum height?

Hint 1. Motion of ball at the top.

At the maximum height, is the ball moving upward or downward? If neither, describe what the ball is

It stays the same.

It decreases.

It increases.

It increases.

It stays the same.

It decreases.



doing.

ANSWER:

Correct

Part E

How does the acceleration of the ball change when the velocity at which it is thrown upward is increased?(Note: the acceleration graph is shown in red.)

Hint 1. The cause of acceleration.

The acceleration of the ball is due to Earth’s gravitational pull. It has nothing to do with the directionin which the ball is moving.

ANSWER:

Correct

Part F

What is the acceleration of the ball when it is moving up, when it is at the maximum height, and when it ismoving down? (Note: The acceleration graph is shown in red.)

Hint 1. The cause of acceleration.

The acceleration of the ball is due to Earth’s gravitational pull. It has nothing to do with the directionin which the ball is moving.

ANSWER:

It is always positive.

It is either positive or negative, depending on the initial velocity.

It is always negative.

It is always zero.

It increases.

It stays the same.

It decreases.



Correct

Correct answer! In fact, the acceleration due to gravity is always 10 m/s2 downward. In other words, it

is -10 m/s2.

Video: Air Resistance and Falling Objects

Watch the video and then answer the following questions.

Part A

In the video, Dr. Hewitt drops a book and a flat piece of paper together from the same height. Which objectthat hits the ground first?

Hint 1. Air resistance on the object

Think about which object will experience a greater air resistance relative to its weight when it drops.

It is always negative.

It is always zero.

The acceleration is positive when the ball is moving up, zero at the top, and negative when theball is moving down.

The acceleration is negative when the ball is moving up, zero at the top, and positive when theball is moving down.

It is always positive.



ANSWER:

Correct

Part B

In the video, Dr. Hewitt drops a book and a flat piece of paper together from the same height, and oneobject hits the ground before the other. Why does that object hit the ground first?

Hint 1. Air resistance on the object

Think about which object will experience a greater air resistance relative to its weight when it drops.

ANSWER:

Correct

Part C

When Dr. Hewitt drops a book and a crumpled piece of paper together from the same height, which onehits the ground first?

Hint 1. If gravity were the only force

Think about how the objects would fall if gravity were the only force.

ANSWER:

The book and paper hit the ground at the same time.

The book hits the ground first.

The paper hits the ground first.

The heavier object hits the ground first because it experiences a greater force of gravitationalattraction from Earth.

The lighter object--the paper--hits the ground first because lighter objects have lower inertia andmove more easily than heavier objects.

The heavier object--the book--hits the ground first because the other, lighter, object is moreinfluenced by air resistance.

The lighter object--the paper--hits the ground first because it easier for gravity to influence itsmotion.

Both objects strike at the same time because the heavier object experiences greatergravitational force, but it also has greater inertia. The lighter object has less gravitational force,but it also has smaller inertia.



Correct

Part D

When Dr. Hewitt drops a book and a crumpled piece of paper together from the same height, which objecthits the ground first, and why?

Hint 1. Comparing air resistance on the objects

Think about how crumpling the piece of paper changed its air resistance.

ANSWER:

Correct

Part E

Based on the experiment that Dr. Hewitt demonstrated in the video, what factors determine whether the airresistance experienced by a falling object will affect the motion of the object?

Hint 1.

Compare the two situations: one involving the flat sheet of paper and the other involving thecrumpled paper. What is different about those two situations?

ANSWER:

They both hit the ground at the same time.

The crumpled paper hits the ground first.

The book hits the ground first.

The lighter object--the crumpled paper--hits the ground first because it is easier for gravity toinfluence its motion since it is light.

The heavier object--the book--hits the ground first because it experiences a greater force ofgravitational attraction from Earth.

Both objects hit the ground at the same time because air resistance is negligible.



Correct

Score Summary:

Your score on this assignment is 74.7%.You received 2.99 out of a possible total of 4 points.

The area of the object in relation to the weight of the object determines the air resistance theobject experiences. Objects having greater area but smaller weight experience greater effect ofair resistance.

The area of the object alone determines whether the air resistance it experiences will have agreater effect on the motion. Objects having smaller area experience greater air resistance.

The weight of the object alone determines whether the air resistance it experiences will have agreater effect on the motion. Heavier objects experience greater effects due to air resistance ontheir motion.

mastering physics- kinematics lab

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