1. Newton’s Laws of Motion
AP Physics Unit 2 Section 1
Newton’s Laws
Lesson 1

2. Do Now: What is the acceleration on a F-150 (mass = 1500
Do Now: What is the acceleration on a F-150 (mass = Kg) if it starts from rest and reaches 25.0 m/s {about 55 mph} in 6.50 seconds? What is the “Force” needed to attain this acceleration?
Objectives:
1st Law: Inertia
2nd Law: F = ma
3rd Law: Equal and Opposite
Homework:
TBA

3. Isaac Newton
Born 1642
Went to University of Cambridge in England as a student and taught there as a professor after
Never married
Gave his attention mostly to physics and mathematics, but he also gave his attention to religion and alchemy
Newton was the first to solve three mysteries that intrigued the scientists
Laws of Motion
Laws of Planetary Orbits
Calculus

4. Three Laws of Motion Newton’s First Law: Law of Inertia
Newton’s Laws of Motion are laws discovered by Physicist and mathematician, Isaac Newton, that explains the objects’ motions depending on forces acted on them
Newton’s First Law: Law of Inertia
Newton’s Second Law: Law of Resultant Force
Newton’s Third Law: Law of Reciprocal Action

5. Newton’s First Law: Inertia NO “net” acceleration
An Object at rest remains at rest, and an object in motion continues in motion with constant velocity (that is, constant speed in a straight line), unless it experiences a net external force.
The tendency to resist change in motion is called inertia
People believed that all moving objects would eventually stop before Newton came up with his laws

6. Newton’s First Law
When there is no force exerted on an object, the motion of the object remains the same like described in the diagram
Because the equation of Force is F=ma, the acceleration is 0m/s². So the equation is 0N=m*0m/s²
Therefore, force is not needed to keep the object in motion, when
The object is in equilibrium when it does not change its state of motion

7. Newton’s Second Law: Force “net” acceleration
The acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass
anet = Fnet / mass or
F = ma
Fnet
Acceleration

8. Force Two types of forces Contact force Field force
Force caused by physical contact
Field force
Force caused by gravitational attraction between two objects
Force caused by electromagnetic attraction between two objects

9. Friction A force that causes resistance to motion
Arises from contact between two surfaces
If the force applied is smaller than the friction, then the object will not move
If the object is not moving, then ffriction=Fapplied
The object eventually slips when the applied force is big enough

10. Friction
Friction was discovered by Galileo Galilee when he rolled a ball down a slope and observed that the ball rolls up the opposite slope to about the same height, and concluded that the difference between the initial height and the final height is caused by friction.
Galileo also noticed that the ball would roll almost forever on a flat surface so that the ball can elevate to the same height as where it started.

11. Two types of Friction Static Friction
Friction that exists while the object is stationary
If the applied force on an object becomes greater than the maximum of static friction, then the object starts moving
fstatic≤μstaticn
Kinetic Friction
The friction that exists when an object is in motion
F-fkinetic produces acceleration to the direction the object is moving
If F=fkinetic, then the object moves at constant speed with no acceleration
fkinetic= μkineticn
Kinetic friction and the coefficient of kinetic friction are smaller than static friction and the static coefficient

13. The car is traveling rightward and crashes into a brick wall
The car is traveling rightward and crashes into a brick wall. The brick wall acts as an unbalanced force and stops the car.

14. The truck stops when it crashes into the red car.
But the ladder falls in front of the truck because the ladder was in motion with the truck but there is nothing stopping the ladder when the truck stops.

15. Unbalanced Force and Acceleration
Force is equal to acceleration multiplied by mass
When an unbalanced force acts on an object, there is always an acceleration
Acceleration differs depending on the net force
The acceleration is inversely related to the mass of the object

16. Net Force Force is a vector
Because it is a vector, the net force can be determined by subtracting the force that resists motion from the force applied to the object.
If the force is applied at an angle, then trigonometry is used to find the force
Fnet

17. R R θ θ
R*sin θ
R*cos θ

18. Gravitational Force
The force that exerts all objects toward the earth’s surface is called a gravitational force.
The magnitude of the gravitational force is called weight
The acceleration due to gravity is different in each location, but 9.80m/s² is most commonly used
Calculated with formula w=mg

19. Newton’s Third Law
If two objects interact, the force exerted on object 1 by object 2 is equal in magnitude but opposite in direction to the force exerted on object 2 by object 1
Forces always come in pair when two objects interact
The forces are equal, but opposite in direction Fn Fg

20. Newton’s Third Law
As the man jumps off the boat, he exerts the force on the boat and the boat exerts the reaction force on the man.
The man leaps forward onto the pier, while the boat moves away from the pier.

21. Newton’s Third Law Force exerted by the road
Force exerted by the wheels
Force exerted by the road

22. Newton’s Third Law
Flow pushed backward
Foil deflected down

23. Works Cited Henderson, Tom. Physics. Course home page. 16 May 2008
Serway, Raymond A., and Jerry S. Faughn. "The Laws of Motion." College Physics .      Fifth ed
Benson, Tom. Newton’s Third Law applied to Aerodynamics 21 May
Introduction to Rocket Performance. Newton’s Third Law. 12 March
Stern, David P. (16) Newton’s Laws of Physics. 1. Force and Inertia. 9 October