**Brainstorm**

I clickers

**Research**

**Motion in 1-D**

**Notes**

Kinematics

Vectors

Components

Important

Details

(cc) photo by Metro Centric on Flickr

(cc) photo by Franco Folini on Flickr

(cc) photo by jimmyharris on Flickr

Forces!!!

(cc) photo by Metro Centric on Flickr

NEWTON's

LAWS

1st Law

2nd Law

F=ma

if F = 0

then a = o

and v = ?

Static Equilibrium

Dynamic Equilibrium

gravity & weight

mass = Weight

NO! NO! NO!

Apparent Weight

Equilibrium

Weight

F=ma

Equilibrium

Sum of forces = Zero

Static

Velocity also = zero

NOT MOVING

Dynamic

Velocity is constant

IS MOVING

Note:

Only works on a particle model, just a dot,

we'll deal with rods and massive objects later

bird sits in the middle of a telephone wire

(5 ounce bird with a 1lb coconut, gripped by the husk)

The 1kg bird depresses the massless wire by 10 degrees, what is the tension of the wire?

Using F=ma

Two steps:

1. Find Acceleration

2. Use kinematics to find motion

Components, Components, Components

Lots of Algebra

Free body diagrams

Use acceleration in equations

Hints: Look for knowns (time, distance, velocities)

Repeat same steps

each time, always!!

500 g model rocket blasts off with 20.0 N of steady

thrust from the little engine, which lasts for 5 seconds.

How High does it go? (ignore weight loss, and air resistance)

Weight, Gravity, Mass

Newton's law of gravity

Yet we have said F = mg

G

Weight w = mg

ALWAYS

What about elevators?

- An apparent weight!

Standing on a bathroom scale in an elevator,

Joe Bob, notices that he has a weight that is

75% his normal weight, just as the elevator begins its descent. How fast is it accelerating?

Examples

Take a closer

Look

SUM it all up!!

QUIZ

TIME

If an objects Net Force

is Zero then

A. Its not moving

B. It has constant velocity

C. Either / or Depends

In using Newton's Laws in

problems it is good to use:

A. FBD

B. Vector Components

C. Algebra

D. Kinematic equations

E. All the above, in order!!

If I wanted to have an apparent weight double my normal weight

what should my acceleration be?

A. 2 g

B. g

C. 0

D. -g

E. -2g

(g can change though)

"Could you please go over static vs dynamic equilibrium?"

" Can we go over the figure 6.1 with the man weighing himself in the accelerating elevator?"

"Is it appropriate to say "apparent weight" when talking about objects accelerating? "

" how do we measure mass?"

"Why is the cup "Accelerating" with the astronaut? from the pre-quiz questions?"

A student stands on a scale in an elevator that is accelerating at 2.5 m/s2. If the student has a mass of 78 kg, to the nearest newton what is the scale reading?