108 Newton’s Second Law Notes 107

11/20/2014Starter:

11/20/2014

Practice/Application:

Glue here when done

Newton’s Second Law Notes

Connection:

Calculations. Turn in when complete

Copy Triangle here

Exit:What is the force exerted when a 5kg bowling ball is dropped on a toe?

Force or No Force? Two friends observe a piece of paper that falls from a 5 story building. The friends disagree about whether forces were acting on the piece of paper. This is what they say: Jorge: “I think things have to touch in order to have a force between them, so no forces were acting on that piece of paper.” Sarika: “I don’t think things have to be touching to have force between them, so I do think forces were acting on the piece of paper.” Which friend do you agree with? ____________ Explain your thinking. Provide examples that support your ideas about forces.

November 20, 2014AGENDA

8.6 CStudents will investigate and describe applications of Newton’s by reading and writing during an activity.

1 Starter2. Notes3. Activity4. Exit

Force = mass x acceleration

F

am X

÷÷

Force = newtons (N)

mass = grams (g)

acceleration = (m/s/s )or

(m/s2)

Date Lecture/ Activity/ Lab Page

Table of Contents

11/3 Speed, Velocity, and Acceleration Notes 87-8811/4 Speed and Velocity Lab 89-9011/5 Interpreting Graphs 91-9211/6 Walking Lab II with graphing 93-9411/10 Balanced and Unbalanced Forces 95-9611/12 Newtons 1st Law 97-9811/13 Newton’s First Law Lab 99-10011/14 Newton’s First Law Writing 101-10211/17 CBA review 103-10411/19 Newton’s First Law Lab #2 105-10611/20 Newton’s Second Law 107-108

Newton’s Second

Law TEKS 8.6A demonstrate and calculate how unbalanced forces change the speed or direction of an object’s motion

TEKS 8.6C investigate and describe applications of Newton’s law of force and acceleration

Net Force, Mass and Acceleration

Isaac Newton discovered one of

the most important laws of nature; the

relationship between net force, mass (inertia) and

acceleration.

Newton’s second law states that the net force acting on a

mass causes the mass to accelerate in the direction of the net

force.

A shorthand way of writing this law is:

f = ma

f = force in newtons (N)m= mass in kilograms (kg)a = acceleration in meters per

second per second (m/s2)

Objects with more mass are more

difficult to accelerate.

If the same force is

applied to two objects

with different masses, the one with the smaller mass

will accelerate

more.

More mass means less

acceleration, unless a

larger force is applied.

small mass

leads to

large mass

leads to

large acceleration

Same Forces

small acceleration

small mass

can lead to

large mass

same acceleration

small force

large force

Different Forces

Falling Objects and Newton’s

2nd Law

Galileo Galilei, the

Italian physicist

and astronomer,

studied falling

objects.

He found that when two objects of different

masses are dropped, they

fell at the same rate.

This was never fully understood

until Isaac Newton announced his second law of

motion.

In the case of free falling objects, the

force is equal to the weight of the object, which is

determined by the acceleration of

gravity (9.8 m/s2).

Try dropping a book and a ball of paper. See what

happens.

Now try dropping a piece of paper and

a book.

Most likely you will see that the paper falls more

slowly.

Remember the book has more weight than the paper, so it has more force to

resist friction from the air.

Try dropping the book with the paper against

the lower surface of the book.

What happens?

Now try dropping the book with the

paper on top of the book.

How will the accelerations of the book

and the paper

compare?

Will they separate and fall

differently?

How much force will be required to move the

object in each picture?

2 m/s2 m=50kg

f =

m=2000 kg

.05 m/s2

f=

100N

100N

What direction are the forces applied in

each picture?

2 m/s2 m=50kg

f =

m=2000 kg

.05 m/s2

f=

left

right

Will the rock and the van accelerate at the

same rate?

2 m/s2 m=50kg

f =

m=2000 kg

.05 m/s2

f=

No, the rock will accelerate faster.

108 Newton’s Second Law Notes 107

11/20/2014Starter:

11/20/2014

Practice/Application:

Glue here when done

Newton’s Second Law Notes

Connection:

Calculations. Turn in when complete

Copy Triangle here

Exit:What is the force exerted when a 5kg bowling ball is dropped on a toe?

Force or No Force? Two friends observe a piece of paper that falls from a 5 story building. The friends disagree about whether forces were acting on the piece of paper. This is what they say: Jorge: “I think things have to touch in order to have a force between them, so no forces were acting on that piece of paper.” Sarika: “I don’t think things have to be touching to have force between them, so I do think forces were acting on the piece of paper.” Which friend do you agree with? ____________ Explain your thinking. Provide examples that support your ideas about forces.