Take out your lab paper from last week. You may discuss with a partner but you must write down your own responses

How did you find the acceleration of the cart in this lab?

The acceleration of the cart was the same as what other object in the lab?

How did you calculate Fnet? Which mass did you use to find Fnet? Why?

Reminder: Newton’s Second Law Labs will be due Tuesday October 26. Please come in for coach class if you need help!!!

Do Now: on a new sheeet – take out your last Do Nows to turn in!!!

1.What does the word “force” make you think of?

2.What are some ways you have used the word “force” in your life?

Do Now (11/17):

New Unit: Newton’s Laws

An object at rest will stay at rest or in constant straight line motion (a=0) UNLESS acted on by a nonzero net force

Newton’s 1st Law: (fill in appropriate spaces on your graphic organizer)

An object is accelerating if it is EITHER changing speed and/or changing direction (ex. A car making a right turn but keeping the same speed)

*Note

the tendency of an object to resist a change in motion. This is quantified by its mass.

Inertia: (fill in appropriate spaces on your graphic organizer)

Imagine you are standing in a stationary bus. Suddenly the bus starts moving. What happens?

Example:

You fall backwards! This is due to the inertia of your body. When the bus was at rest, you were also at rest. When the bus started moving, your legs went with the floor of the bus due to friction. But the upper part of your body tends to continue in its state of rest (inertia of rest). As a result you fall backwards.

Example:

Braking in a car: Hopefully you'd be wearing your seat belt because that would be the outside force. The seat belt stops you from flying through the windshield. If not, then the windshield is the outside force slowing you down.

Turning in a car: That is inertia because your body wants to go straight but the outside force (aka the car) is turning you.

More Examples:

Dice in your rearview mirror

An object which is accelerating has a nonzero net force acting on it equal to the object’s mass times its acceleration.

i.e. F = ma

Newton’s 2nd Law: (fill in appropriate spaces on your graphic organizer)

The same force exerted on a larger mass produces a smaller acceleration.

Force is measured in Newtons, represented by a capital N

1 N = 1 kg x m/s2

One Newton is approximately 7 Fig Newtons

Calculating Force

a=5 m/s2, m = 4 kgF = ?

Calculating Force:

F = ma = (5 m/s2)(4 kg) = 20 N

A golfer applies a force of 6 N to a 0.5 kg golf ball. What is the ball’s acceleration?

Calculating Acceleration:

F = ma a = F/m

a =F/m=(6 N)/(0.5 kg)=12 m/s2

Use the rest of class to work on the worksheet “Newton’s Laws.” It will be due on Monday 11/21/11

Practice:

1. A baseball pitcher throws a ball by applying a force of 25 N to it. The ball accelerates at 50 m/s2 . What is the ball’s mass?

2. You are standing on a moving bus when it suddenly brakes. Describe what happens and why.

Do Now: ( 5 min)

Read the article: “As Injuries Rise, Scant Oversight of Helmet Safety” on www.nytimes.com (you may have to search for it)

Write as detailed a description of the article as possible explaining how concepts we have talked about in physics class appear in this investigation. The longer and better the description, the more points!!!

Extra Credit Opportunity

A force is any influence that causes an object to accelerate (usually a push or pull)

Forces are vector quantities

We can represent them by drawing a force vector

Every force vector should have an arrowhead a tail and a label

Forces

Symbol: Ff

Definition: The contact force that opposes sliding motion between surfaces

Friction

Ff

Symbol: FN

Definition: the contact force exerted by a surface on an object

Normal Force

FN

Symbol: FT

Definition: the pull exerted by a string, rope, or cable when attached to a body and pulled taut

Tension FT

Symbol: Fthrust

Definition: a general term for the forces that move objects such as rockets, planes, cars and people

Thrust

Symbol: Fg

Definition: a long-range force due to gravitational attraction between two objects, generally earth and an object

Weight

Fg

Reminder – ID’s!!!!!!!!

Use the rest of class to fill in your chart. You may use classroom textbooks (p. 123) to help you.

After you have finished your chart, you may continue working on your homework (Newton’s Laws Worksheet)

Practice

Fill in the force vectors in the following diagrams. Be sure to include ALL forces!!!

Do Now (5 min)

1.

2. (a ball rolling down a hill)

A car traveling at 60 mph

Weight is the force of gravity (represented by Fg)

Fg=mg where m=mass and g=acceleration due to gravity (on earth: -9.8 m/s2)

The Force of Gravity!!! (aka Weight)

MASS AND WEIGHT ARE NOT

THE SAME THING!!!!!!

!!!!

Step 1: Write down your weight in pounds. If you don’t know your weight or don’t want to write it, make something up.

Step 2: To convert your weight into Newtons, multiply your weight in pounds by 4.448221 or 4.45

Step 3: Write that weight in the weight column next to “Earth”

Step 4: Follow the directions on the rest of the worksheet.

Gravity, Weight, and Mass Activity

Follow the directions on the rest of the worksheet.

*reminder – MASS DOES NOT CHANGE THROUGHOUT THE UNIVERSE!!!!!!

Gravity, Weight, and Mass Activity

Write down everything you know about regular ole parallel circuits.

Do Now (12/16):