U2 - Balanced forces packet

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Name:__________________ Period:______Date:_______

Life…my friends…is all about finding balance.

~Unit 2: Balanced Forces~ Essential Questions:

1) What is a force, and how can it be described? 2) How is force connected to motion?

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Activity 1 Name:__________________ Period:______Date:_______ I need to know how to access the force!

U2 EQ1- Forces:

What is a force, and how can it be described?

Activities that support the essential question:

Objectives Investigations Formative

grade

I’m just getting started

I’m on my way

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I can categorize forces.

______ / 1 2 3 4 5 I can describe forces using

on/by notation. ______ / 1 2 3 4 5

I can draw a force diagram with no missing or extra forces.

______ / 1 2 3 4 5

Reinforcement and enrichment options:

Activity Date completed Did this help your

understanding?

Next step for you

For forces: Read pages 87-89 in your text. (Section 4.1: Force and Motion)

Y / N

For on / by notation: Read page 102 (Identifying

interaction forces) Y / N

Watch the review video on Force Identification and on/by notation

Y / N

Come in and talk with a

Mr. C! Y / N

Essential question self-reflection:

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I’m just getting started

I’m on my way

I am at peace with this stuff Reflection on essential question: What is a force, and how can it be

described? 1 2 3 4 5

Write any further questions that you still have in the space below:

Activity 2 Name:__________________

Period:______Date:_______ I need to know what to call the force so I don’t upset it!

U2 EQ2- Forces:

How is force connected to motion?

grade I’m just getting started

I’m on my

way I am at peace with this stuff I can recognize balanced

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I can show balanced and unbalanced forces using

force diagrams. ______ / 1 2 3 4 5

I can use forces to explain why a particular motion occurs (constant or changing motion)

______ / 1 2 3 4 5

understanding?

Next step for you

For balanced forces: Read pages 102-107.

(Newton’s 3rd_{law, forces}

of ropes and strings, and the normal force)

Y / N

For unbalanced forces: read pages 90-92 (Force and acceleration)

Y / N

Watch the review video on balanced and

unbalanced forces

Y / N

physics teacher! Y / N

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I’m on my way

I am at peace with this stuff Reflection on essential question: How is force connected to motion?

1 2 3 4 5

Activity 3 Name:__________________

Period:______Date:_______ The force tries to keep secrets from me…but I can see where the force is headed! U2 EQ3 - Forces:

What are the keys to solving quantitative balanced force

problems?

grade

I’m just getting started

I’m on my way

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(without extra forces or missing forces)

I can use a force diagram to solve for unknown forces in one dimension.

______ / 1 2 3 4 5

I can use a force diagram to solve for unknowns in two dimensions.

______ / 1 2 3 4 5

understanding? Next step for you For ‘force diagrams’ and

problem solving: Read pages 102-107.

(Newton’s 3rd_{law, forces}

of ropes and strings, and the normal force)

Y / N

Watch the review video on balanced and

unbalanced forces

Y / N

physics teacher! Y / N

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I’m on my

way I am at peace with this stuff Reflection on essential question: What are the keys to solving

quantitative balanced force problems? 1 2 3 4 5

Activity 4 I cast thine ballot for big-e-smalls! ~U1A1: Vector Voting~

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Activity 5 Name:__________________ Period:_____Date:________

May the forces be with you.

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Kinds of forces Description / details about each force

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Activity 6 These invisible forces…what do they do? U1N2 – Force diagrams

Situation 1: Falling Book

Force Diagram: Motion/Force Description:

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Situation 2: Book at rest on desk

Situation 3: Book being pushed, but not going anywhere

Based on the three examples so far, I would say that: 1. When forces are balanced, the object…

2. When forces are unbalanced, the object…

Situation 4: Book sliding across the desk, after the push by the hand, before it comes to rest

Force Diagram: Motion/Force Description: Physics Book

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Situation 5: Air puck sliding across the floor, after the push by the hand, before it comes to rest Force Diagram: Motion/Force Description:

These last two examples demonstrate that a more complete description of the connection between force and motion is that:

1. When forces are balanced, the object…does not change its motion.

2. When forces are unbalanced, the object…changes its motion.

Discussion Summary

1. How will we identify motion that is changing?

2. How will we identify motion that is constant?

3. What does changing motion tell us about the forces on an object?

4. What does constant motion tell us about the forces on an object?

5. Which two demos best support the idea that balanced forces connect with motion that does not change? Explain the connection.

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Activity 7 Name:__________________ Period:______Date:_______

Yo are you moving or are you going to sit there all day?

~U1W1 – Recognizing balanced and unbalanced forces~

Look at the following scenarios and decide what the motion of the object will be. Secondly, draw in force vectors (arrows) that depict the motion you decided on.

First attempt Corrections / solutions / notes

(side view)

Scenario 1: A book lies motionless on a desk

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(side view)

Scenario 2: A book falling off a desk

(side view)

Scenario 3: A book on a desk sliding to the right with

friction (so it is slowing down)

(side view)

Scenario 4: A book on a desk sliding to the right

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Scenario 5: A kid is hanging (still) from a rope swing

Scenario 6: A kid on a sled gets pulled to the right

with friction, and he moves at a constant speed.

Activity 8 Name:__________________

Period:______Date:_______

Gravity – I will find out your value!!!

~U2L1 – The relationship between mass and weight~

We are very familiar with the concept of weight. However, the weight we are familiar with uses the

‘english’ scale. During this lab, we will get more familiar with the metric measurement of weight, and also how weight relates to mass.

Brainstorm: How can we set up an experiment to discover the relationship between mass and weight?

Some questions to guide your thinking:

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What data do we need to collect? How will we collect this data?

How will we gain confidence in our results?

Will drawing a picture help?

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Activity 9 Name:______________________ Period:________Date:___________

Using your Mathematical Model

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2. Determine the gravitational force on a 2.3 g mass by the earth.

3. Determine the gravitational force on a 2300 g mass by the earth.

4. Determine the gravitational force on a 67 kg person by the earth.

5. Determine the mass of a person with a weight (gravitational force on earth) of 600N.

6. If a person with a weight (gravitational force on earth) of 778N weighs 175 lbs, what is their mass?

Activity 10 Name:__________________

Period:_______Date:______

Bring in the numbers chief!

~U2W2 – Problem solving with balanced forces~

1. Gymnast hanging on rings (the ropes are vertical)

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2. A 25 N box sliding on the floor and

slowing down due to friction Draw the Force Diagram Below, fill in themissing force(s) with values Fg on gymnast

by Earth = 800N

Ff on box by

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4. Air hockey puck sliding to the right with constant velocity

Draw the Force Diagram Below, fill in the missing force(s) with values

5. Skydiver falling at constant velocity Draw the Force Diagram Below, fill in the missing force(s) with values

FA on box by

person = 200N FN on box by

Floor = 200N

Fg on puck by

Earth = 12N

FN on skydiver by

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6. Book at rest on an encyclopedia, draw a force diagram of the book on top

7. Lamp hanging from the ceiling Draw the Force Diagram Below, fill in the_{missing force(s) with values}

8. Box on the floor being pulled to the right at constant velocity with friction

Encyclopedia

Fg on book by

Earth = 22N

Fg on Lamp by

Earth = 240N

FA on box by

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Activity 11 Name:__________________

Aparecium! (Surely hoping there is invisible ink on this page)

~U2W3: Problem solving with balanced force problems take 2~

1. Box at rest on the floor, mass of box is 35kg

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2. Box sliding on the floor and slowing

down due to friction, mass of box is 24kg Draw the Force Diagram Below, fill in themissing force(s) with values

Ff on box by

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4. Air hockey puck sliding to the left with

constant velocity, mass of puck = 2 kg Draw the Force Diagram Below, fill in themissing force(s) with values

5. Skydiver falling at constant velocity, mass of skydiver = 105 kg

6. Two books at rest on encyclopedia. Mass of encyclopedia = 3kg, mass of middle book = 3.5kg, mass of top book = 2.0 kg

Draw the Force Diagram for the middle book below, filling in the missing force(s) with

values FA on box by

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7. Lamp hanging from the ceiling, mass of

lamp is 6 kg Draw the Force Diagram Below, fill in themissing force(s) with values

8. Box on the floor being pulled to the right at constant velocity with friction, mass of

box = 11 kg

Top Book Middle Book Encyclopedia

FT on box by

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Group members present: _________________________ ________________________ _________________________ ________________________ Instructions:

This is a summative evaluation. You should work only with the members of your lab group.

A 1000 g mass rests on top of a balance like in the picture below, but the balance does not read 1000 g.

There is tension in the vertical string attached to the mass.

If the reading on the balance is only _____________ g, determine the tension in the string, measured in Newtons.

Show a complete record of the work that led up to your answer on the back of this sheet. 15 points of this lab practical will be for the work you show here. 5 points will be for the accuracy of your prediction based on the scale below.

0-2% 5 points + 2 points of extra credit

2-4% 5 points + 1 point of extra credit

4-6% 5 points

6-8% 4 points

8-10% 3 points

10-12% 2 points

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Activity 13 Name:__________________

I am at one with the universe. That’s right, we are balanced

~Unit 2 Review for Balanced Forces~ Essential Question #1: What is a force, and how can we describe it?

Draw a force diagram for the following objects, making sure to use on/by notation.

1) An object slides to the right at a constant velocity. Force diagram with on/by notation:

2) An object is pulled to the right at a constant velocity.

Force diagram with on/by notation:

3) An object that was thrown into the air and is moving in a parabolic motion (no air resistance)

Force diagram with on/by notation:

4) Superman is attempting to stop a speeding locomotive that is moving at a constant velocity.

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5) The joker is leaning on a cane. (the joker is your

system) Force diagram with on/by notation:

Essential Question #2: How is force connected to motion?

Go over the objects shown above, and check off the characteristics that apply to each: Object Forces are

balanced Forces are unbalanced Motion is constant Motion is changing Object is speeding up Object is slowing down 1

2 3 4 5

If an object has balanced forces, what does that tell you about the motion of the object?

If an object has unbalanced forces, what does that tell you about the motion of the object?

Describe the motion of each object shown below:

Object 1: Motion in the x dimension:

Motion in the y dimension:

Object 2: Motion in the x dimension:

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Essential Question #3: What are the keys to solving quantitative balanced force problems?

What is the ‘magic number’ for gravity, and what is the model that connects the force of gravity to mass?

What is the gravitational force acting on a 75 kg. person?

If the gravitational force on the moon is 1.6 N/kg – what would the weight of the same 75 kg person be on the moon?

What does it mean to say the ∑F = 0?

The object is moving with a constant velocity.

FA

Draw force diagram: Write the equation for ∑Fx:

Write the equation for ∑Fy: If the FA is 30N, what is the Ff?

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An 18 kg mass is sitting on a table, and it is tied to a 11 kg mass that is hanging off the edge of the table. Both of the masses are at rest.

Force diagram for the 18kg mass:

11Kg

Force diagram for the 11 kg mass: Solve for the FN, FA, and the Ff on the 18kg mass.

The hanging Ball A has a mass of 10 kg. The hanging ball B has a mass of 5 kg. Find force in each rope at points 1 and 2.

Force diagram for ball A:

Point 1

Ball A 10 kg

Point 2 Force diagram for ball B:

Ball B 5 kg

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