newton’s laws of motion conservation laws in astronomy
TRANSCRIPT
Newton’s Laws of Motion
Conservation Laws in
Astronomy
Isaac Newton1642 (1643) - 1727
Isaac Newton1642 (1643) - 1727
Invented calculus
Isaac Newton1642 (1643) - 1727
Invented calculus
Studied optics
Isaac Newton1642 (1643) - 1727
Invented calculus
Studied optics
Developed his law of universal gravitation
Newton’s First Law of Motionis also known simply as
“Inertia”
Galileo actually came up with it first.
If there is no net force on an object
a) it doesn't move.
b) its velocity doesn't change.
c) its momentum doesn't change.
d) all of the above
e) b and c
Acceleration is any change in motion
m
Fa
maF
maF m
Fa
A 7.5 N force acts on a 12.5 kg satellite when its thruster fires. What will its acceleration be?
maF m
Fa
As you watch, a 12,000 kg F-16 fighter jet accelerates through the air at 10.6 m/s2. What is the thrust of its engine?
A ball is swung around in circles on a string. Is there a net force on the ball?
A) Yes
B) No
C) It’s not possible to decide without further information.
In this case, the force is always perpendicular to the velocity.
That force will change the direction without changing the speed.
Remember:If velocity changes, there is ALWAYS a non-zero net force.
Newton’s Third Law of Motion
When object 1 exerts a force on object 2, object 2 exerts the SAME force on object 1, but in the opposite direction
Sometimes called “Action – Reaction”
Equal and opposite force pairs
Newton’s Third Law of Motion
Working in space is complicated by Newton’s third law
Newton’s Law Summary
Inertia F = ma Action-Reaction
1 2 3
An astronaut on a space walk outside the International Space Station finds herself 20 m away from the station, sitting perfectly still (with respect to the ISS), with no tether, and her hand-held maneuvering gun is out of fuel. How can she get back to the ISS?
A) She can’t – she’s space toast
B) Throw the maneuvering gun directly away from the ISS
C) Throw the maneuvering gun directly at the Earth
D) Throw the maneuvering gun directly at the ISS
E) Make a swimming motion toward the ISS
Conservation of Momentum
If the net external force on a system is zero, there will be no change in the
system’s momentum.
It takes an external force to change the momentum
of a system.
What external force gave this system its momentum?
Conservation of Angular Momentum
The type of force that can change an object’s angular momentum is called “torque”
Torque is force x distance
Using a wrench increases torque by increasing distance
distance
force
Conservation of Angular Momentum
This has an interesting effect on spinning objects…
Note that there is no net torque on the skater
Her angular momentum is NOT changing
Astro-Cash Cab!
Adrianna Cordova
Tyler Zito
Corey Schatz
Pauline Luhman
Derek DiThomas
1) If a planet travels in a circular orbit without speeding up or slowing down, does it have a force on it?
2) True or False ?
Newton’s First Law of Motion says that the planets travel around the Sun in ellipses, with the Sun at one focus.
3) If a 10 kg object is acted on by a 100 N force, what will its acceleration be?
4) What conservation law explains why a rotating skater speeds up when she pulls her arms in?
Conservation of Energy
Conservation of Momentum
Conservation of Angular Momentum
Conservation of Charge