TODAY

1) Over the weekend/next class: Video up on new information.

TO INFINITY…AND BEYOND! Lets look at rockets for a moment. How in the

heck do they work?

When they work…

How did the rocket go up?

ROCKET SCIENCE, BABY!How the rocket went up…. Lets draw a FBD

with a net force equation:

But where is this force coming from?The ignition of the fuel pushed gas out, which

creates an opposite force pushing the rocket up.

QUESTION FOR YOU ALL

As it’s going up, should the velocity of the rocket increase/decrease or not change if the thrust (engine force) is constant?

OH GOD, ROCKET SCIENCE

So as getting further from Earth, the weight decreases.

The rocket gets lighter too, so it has less mass for the imbalance to accelerate.

More imbalance, less mass to accelerate means more acceleration!

BUT NOT EVERYONE AGREED

BUT IT TURNS OUT IT WORKS

Newtons laws don’t need atmospheric pressures (atm’s) to work.

In outer space, we are in micro-gravity don’t you mean zero gravity?

So you are working on the ISS, and you turn a valve clockwise. What happens to you?

Yeah, you get it. NASA didn’t at 1st

So Newton’s laws work anywhere in the universe*

They will form the basis of how we study motion in almost every situation. Blocks on ramps Masses with pulleys Planets around stars and why they don’t get

sucked into the star* Ice skaters in routines and why they speed up

when their arms go in Bicycle riders and why they don’t fall over if they

start moving. Why running on pavement results in a faster run

(but is more painful on your knees)

THE PHYSICS OF THE RUN Run definition: Both feet off

the ground.

FBD of person of thembefore they start running.

THE PHYSICS OF THE RUN Run definition: Both feet off

the ground.

FBD of person of themas they push off…

There is no normal force ifyou left the ground (since youare pushing up and off)

Which is greater, the weightor the force of them pushingup?

There is an imbalance on them,which by Newtons 2nd Law creates an acceleration. IN THIS CASE…

WHEN YOU COME BACK DOWN TO GROUND You are moving down and then

come to a stop. Is there animbalance?

1st lets draw a FBD of the personhitting the ground

IMBALANCE UP, since you areSLOWING your downwards motion.

WHEN HITTING THE GROUND

If the imbalance is UP, which has more force; the UP or DOWN force?

Our net force equations:

Where do we feel this force?

EVEN IN SPACE

It all ties in together.

Water in space… The water molecules all pull on eachother

until they equalize into a max volume/min surface area arrangement: A sphere.

Which mimicks planet formation in a special way, and possibly the first cellular life.

Oh yeah

AN EXAMPLE…

A panda is lifting a 10kg child up at a constant velocity. How much force is he applying to the child?

Is there an imbalance? Is he lifting MORE/LESS/EQUAL to the weight?

AN EXAMPLE…

A panda is lifting a 10kg child up, and is accelerating the child at 2m/s2. How much force is he applying to the child?

Is there an imbalance? Is he lifting MORE/LESS/EQUAL to the weight?

AN EXAMPLE…

A panda is lifting a 10kg child up, but the child is slowing at a rate of 2m/s2. How much force is he applying to the child?

Is there an imbalance? Is he lifting MORE/LESS/EQUAL to the weight?

TO DA BOARDS.