Survey

* Your assessment is very important for improving the work of artificial intelligence, which forms the content of this project

Document related concepts

Specific impulse wikipedia, lookup

Atomic theory wikipedia, lookup

Quantum vacuum thruster wikipedia, lookup

T-symmetry wikipedia, lookup

Newton's theorem of revolving orbits wikipedia, lookup

Theoretical and experimental justification for the Schrödinger equation wikipedia, lookup

Photon polarization wikipedia, lookup

Classical central-force problem wikipedia, lookup

Work (physics) wikipedia, lookup

Electromagnetic mass wikipedia, lookup

Equations of motion wikipedia, lookup

Angular momentum wikipedia, lookup

Rigid body dynamics wikipedia, lookup

Classical mechanics wikipedia, lookup

Angular momentum operator wikipedia, lookup

Accretion disk wikipedia, lookup

Seismometer wikipedia, lookup

Modified Newtonian dynamics wikipedia, lookup

Force wikipedia, lookup

Buoyancy wikipedia, lookup

Center of mass wikipedia, lookup

Weight wikipedia, lookup

Friction wikipedia, lookup

Relativistic angular momentum wikipedia, lookup

Momentum wikipedia, lookup

Inertia wikipedia, lookup

Relativistic mechanics wikipedia, lookup

Gravity wikipedia, lookup

Newton's laws of motion wikipedia, lookup

Transcript
```Unit 5 – Lecture 5
Newton’s Third Law
Newton’s Third Law – cont’d
 For every action, there is an equal but opposite
reaction.
 these forces are acting on
different objects, so they
are not balanced forces
[balanced forces act
on the same object]
Forces and Vectors
Gravity
 Gravity - a force of attraction between all objects
which have mass
 it is inherent to all matter
 depends on:
 distance between the masses
 “inverse square” law – physical quantity or
strength is inversely proprotional to the square
of the distance from that source of the physical
quantity
 size of the masses
Gravity
Mass vs. Weight
 Mass – the measure of the amount of matter in an
object.
 measures the inertia of an object
[more mass, more inertia / less mass, less inertia]
 Weight – the force of attraction caused by gravity
acting on a mass.
 Fw = m*g
 “g” refers to our gravity
 on Earth, g = 9.8m/s2
Mass vs. Weight – cont’d
 We use weight and mass interchangeably because the
only comparison we have is the Earth’s gravity.
 Weight will change based on local gravity; NASA has
to take this into effect
 example: Susie weighs 125 lbs on Earth. She weighs:
 20.7 lbs on the moon
 295.5 lbs on Jupiter
 47.1 lbs on Mars
 8.3 lbs on Pluto
Practice:
Fw = m*g
 How much does a 25 kg object weigh in Newtons?
 245 N
2.6 N
0.392 N
 If an object weighs 397 N, what is its mass?
 0.02 kg
3890.6 kg
40.5 kg
 If an object weighs 1100 N but has a mass of 125 kg,
which planet is it on?
 Venus, g = 8.8 m/s2
Mars, g = 3.7 m/s2
Jupiter, g = 24.8 m/s2
Friction
 Friction is the force that opposes all motion.
 A moving object will always lose energy to friction
Friction – cont’d
 Three Types of Friction:
 Sliding Friction



when two surfaces slide along each other
most resistive friction / requires the most force
can lead to buildup of heat
Friction – cont’d
 Three Types of Friction:
 Rolling Friction


when an object or surface rolls along another
less resistive than sliding, more resistive than
fluid
Friction – cont’d
 Three Types of Friction:
 Fluid Friction


solid surfaces sliding with a
layer of liquid or gas between them
[layer fills in the tiny
depressions on surfaces
least resistive friction –
requires the least force
 lubrication
 air resistance
Practice
 What type of friction is exhibited by your shoes on the
ground?
 sliding
 What type of friction is exhibited by a lubricant?
 fluid
 What type of friction is exhibited by the wheels on a
cart?
 rolling
Momentum
 Momentum - the product of an object’s mass
multiplied by its velocity
 p [momentum] = m [mass] * v [velocity]
 p = kg * (m/s) = kg*m/s [kilogram meters per second]
Practice
 What is the momentum of a 210 kg hog
running at 12 m/s?
 17.5 kg*m/s
 2520 kg*m/s
 0.057 kg*m/s
Momentum – cont’d
 Law of Conservation of Momentum –
momentum can not be created or destroyed under
normal circumstances
 it can be changed from one form to another
 total momentum before = total momentum after
 ex: pieces of a dropped light bulb, etc.
Law of Conservation of Momentum
 Formula
 object 1 initial momentum + object 2 initial momentum
equals
 object 1 final momentum + object 2 final momentum
 p1i+ p2i = p1f + p2f
(m1vi+m2vi = m1vf+m2vf )
Conservation of Momentum
&Newton’s Laws
 An untethered astronaut is stranded away from his
spaceship while working on a satellite in space. The
only equipment he has is all the tools he was using to
repair the satellite.
 Discuss with a partner what he could do – according to
these two laws – to get back to the ship.
Conservation of Momentum
& Newton’s Laws
 If the astronaut were to throw a piece of equipment
away from the spaceship, he would gain a small
amount of momentum in the direction of the
spaceship (Newton’s 3rd Law).
HOMEWORK
 complete
 page 17
 Newton’s Laws w/s
```
Related documents