A brief review.

• Force.– A push or a pull.

• ‘Nuff said...

No longer review..

• Net force.– The overall force on an object after all forces

are added together.

No longer review..

• Unbalanced forces acting on an object will change the objects motion.

No longer review..

• Balanced forces on an object will not change an objects motion.

Kind’a stupid example 1

Net Force Net Force Net Force= 0

Newton Rocks!

Sir Isaac Newton (1642-1727)

Sir Isaac Newton

“If I have been able to see further, it was only because I stood on the shoulders of giants.”

As mathematician, Newton invented integral calculus, and jointly with Leibnitz, differential calculus. He also calculated a formula for finding the velocity of sound in a gas which was later corrected by Laplace.

Newton made many contributions to astronomy. He defined the laws of motion and universal gravitation which he used to predict precisely the motions of stars, and the planets around the sun. Using his discoveries in optics Newton constructed the first reflecting telescope.

Sir Isaac Newton

Before Newton, science seemed a hodgepodge of isolated facts and laws, capable of describing some phenomena, but predicting only a few. Newton provided science with a system of laws that can be applied to a wide range of physical phenomena, and that can be used to make exact predications. Newton published his works in two books, namely "Opticks" and "Principia."

Newton’s laws

• Newton's First Law of Motion:– Every object in a state of uniform motion tends

to remain in that state of motion unless an external force is applied to it.

– Often termed simply the "Law of Inertia"

Wickedly Cool Example 1!

• Newton’s first law– An object at rest…..

Wickedly Cool Example 2!

• Newton’s first law– An object at rest…..

• tends to stay that way

Newton’s laws

• Newton's Second Law of Motion:– The relationship between an object's mass m,

its acceleration a, and the applied force F is F = ma.

Acceleration and force are vectors (as indicated by their symbols being displayed in slant bold font); in this law the direction of the force vector is the same as the direction of the acceleration vector.

Newton’s laws

• So, if F = ma…..

• Then, a = F/m

Wickedly Cool Example 3!

• Blocks and bands.

Wickedly Cool Lab 1!

• You do it.– Write a Title– Write a hypotheses– Design an experiment– Record results– Conclude experiment

Newton’s laws

• Newton's Third Law of Motion:– For every action there is an equal and opposite

reaction.

Wickedly Cool Example 4!

• Newton’s cradle.

Wickedly Cool Lab 2!

• You do it.– Write a Title– Write a hypotheses– Design an experiment– Record results– Conclude experiment

Levers

• Levers are one of the simple machines that were probably used in prehistoric times. Levers were first described about 260 BC by the ancient Greek mathematician Archimedes (287-212 BC).

Levers

• A lever is a simple machine that makes work easier for use; it involves moving a load around a pivot using a force. Many of our basic tools use levers, including scissors (2 class 1 levers), pliers (2 class 1 levers), hammer claws (a single class 2 lever), nut crackers (2 class 2 levers), and tongs (2 class 3 levers).

Levers

• In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to multiply the mechanical force that can be applied to another object.

Levers

• The lever allows less effort to be expended to move an object a greater distance.

The three classes of levers

• A first-class lever is a lever in which the fulcrum is located in between the input force and the output force.

Class 1 levers

• Examples: #Seesaw (also known as a teeter-totter)

• 1. Crowbar or claw hammer (removing nails)

• 2. Pliers (double lever)

The three classes of levers

• In a second-class lever the input is located to the far side of the bar, the output is located in the middle of the bar, and the fulcrum is located on the side of the bar opposite to the input.

Class 2 Levers

• # Wheelbarrow

• # Nutcracker

• # Door

• # Pry bar

• # Stapler

• # Diving board

The three classes of levers

• Class 3 levers. The input effort is higher than the output load. However, also notice that the input effort moves through a shorter distance than the output load.

The Lever Lab

• To determine how levers change the force required to move an object.

Way Cool Levers

• The trebuchet is a counterweight siege engine. Basically, a lever and a sling.

Trebuchet

• The trebuchet is a Type-1 lever and a sling. In the Type-1 lever, the force is applied to one end, the load is on the other end and the fulcrum sits between the two.

Trebuchet

• The sling is the oldest projectile weapon. There is a pouch to hold the projectile and two long strings. Both ends of the string are held in one hand and the sling is swung around and around. Then, at the proper moment, one end of the sling is let go with the other end is still held by the hand

Trebuchet

Historic Counterweight Trebuchet Illustrations

Trebuchet from The Romance of Alexander (circa 1330).

Historic Counterweight Trebuchet Illustrations

Trebuchet by Kolderer, c1507.

Historic Counterweight Trebuchet Illustrations

An early 14th Century trebuchet

Historic Counterweight Trebuchet Illustrations

A 13th Century "Mongol" trebuchet

Historic Counterweight Trebuchet Illustrations

A fixed-weight trebuchet from the early 16th Century