1. MOTION AND GRAVITY
The key LAWS of the key branch of physics known as MECHANICS were formulated by Isaac Newton
Three LAWS of MOTION
The LAW of GRAVITY
The LAWS of CONSERVATION OF ENERGY and MOMENTUM give a more general way to understand motion
While a physics course would spend the whole first semester on these laws we’ll just get a taste of them!

2. Speed, Velocity and Acceleration
Speed = distance traveled per time (car at 110 km/hr or 70 mph)
Velocity is a speed + a direction (70 mph NE)
Acceleration is a change in velocity per time: speed and/or direction (10 km/s2)

3.  MATHEMATICS AND UNDERSTANDING
Isaac NEWTON ( ) of Woolsthorpe, England is the most important scientist in history.
His work completely changed the way educated people looked at the world. Effectively, Newton was the founder of PHYSICS as well as THEORETICAL ASTRONOMY
HE CO-INVENTED THE CALCULUS (w/ Leibnitz)
HE DID PIONEERING WORK IN
OPTICS: PRISM, REFLECTING TELESCOPE
MECHANICS AND GRAVITY: his Philosophiae Naturalis Principia Mathematica, (pub. 1684) reflected work he'd mostly done in
Newton was knighted, and became first president of the Royal Society, later Director of the Mint.

4. Isaac Newton

5. NEWTON'S LAWS OF MOTION
1. An object at rest remains at rest and an object moving at a certain velocity retains that velocity unless a FORCE acts on it.
Aristotle's view: forces were needed merely to keep something moving at a constant speed
Newton realized friction or air resistance were forces that slowed things down
Galileo had already understood this.

6. Forces Change Velocity
Gravity is a
FORCE that causes downward vertical
acceleration

7. Which of the following is true?
A. You can have acceleration not equal zero, but velocity equal to zero
B. You can have acceleration equal to zero, but velocity not equal to zero
C. You can accelerate without changing your speed
D. A and B.
E. A, B and C.
Answer: E

8. Which of the following is true?
A. You can have acceleration not equal zero, but velocity equal to zero
B You can have acceleration equal to zero, but velocity not equal to zero
C. You can accelerate without changing your speed
D. A and B.
E. A, B, and C.

9. Newton’s SECOND LAW
The core of Newtonian mechanics, it allows trajectories of cannon balls, rockets, planets, comets, stars and galaxies to be computed.
F = m a
is the most important relation in physics; one can equivalently write
a = F/m
This clearly says less massive objects obtain larger accelerations from the same force.
Think of stepping on the gas and going from 0 mph to 60 mph in 10 seconds: your acceleration is 6 mph/s (forwards)
2nd Law Applet

10. Momentum and Force Momentum = mass X velocity (p = mv)
It takes a force to change a body’s momentum
Slightly more general version of Newton’s 2nd Law: F = p/t
Think of a 1000 kg car colliding with a 6000 kg truck head on -- if they have the same speeds the truck has 6 times the momentum and will push the car down the road

11. More on the 2nd Law Breaking takes you from 60 mph back to 0 in 4 sec
or a negative acceleration of 15 mph/s.
These are VECTOR equations -- with magnitude and direction
Velocity = distance covered / time
V = d/t
Acceleration = change in velocity/time change
a= V/t
- both the Speed and Direction are needed
I.e. 50 mph to the East is the same speed, but different velocity, from 50 mph to the North
Going around a curve at a constant speed DOES involve an acceleration (you feel pushed to one side of the car, right?)

12. 3. EVERY ACTION (FORCE) HAS AN EQUAL AND OPPOSITE REACTION.
Newton’s Third Law
3. EVERY ACTION (FORCE) HAS AN EQUAL AND OPPOSITE REACTION.
Forces don't act in isolation:
the Earth pulls the Moon and the Moon pulls back on the Earth;
we push down and back on the ground with our muscles, it pushes us up and forward;
a rower or gondolier pushes water (or canal bottom) in one direction and the scull or gondola goes the other way;
a rocket expels gases rearward and it flies forward.

13. Newton’s Laws of Motion, Illustrated

14. Changing an object’s momentum requires
A. Gravity
B. Applying a force
C. Applying a torque
D. Friction
E. None of the above
Answer: B

15. Changing an object’s momentum requires
A. Gravity
B. Applying a force
C. Applying a torque
D. Friction
E. None of the above

16. Newton’s second law, F = m·a, (force = mass x acceleration), means that with no force,
A. Objects remain at rest
B. An object’s speed doesn’t change
C. An object’s velocity doesn’t change
D. B and C.
Answer: D

17. Newton’s second law, F = m·a, (force = mass x acceleration), means that with no force,
A. Objects remain at rest
B. An object’s speed doesn’t change
C. An object’s velocity doesn’t change
D. B and C