SEISMIC SLEUTHS Part 1Newton’s Laws

EARTHQUAKES AND PHYSICS?

• Newton’s laws • Liquefaction lab • Smart Sitting• Energy and Quakes

CAN BUILDINGS BE MADE SAFER?

• Building Fun• Structural Reinforcement• BOSS• Earthquake in a Box• Building Challenge• Find and Fix the Hazards• Strengthening your

House

Newton’s Laws of Motion:

• 1st Law: Law of Inertia• Objects keep on doing what they are

doing.

http://www.physicsclassroom.com/mmedia/newtlaws/cci.cfm

Mass is directly related to inertia.• The greater the mass the greater the tendency

to resist change of an object’s motion.

• objects will continue to do as they are doing with out friction.

Equilibrium: if the net force on an object is zero (at rest or moving at a constant velocity)

Static friction

• Static friction results when the surfaces of two objects are at rest relative to one another

2nd law: Net force: something that disturbs an

object’s equilibrium (net force changes an object’s velocity or acceleration)

• Need to be able to find the net force (sum of all forces on an object) since net force causes an object’s acceleration

http://www.physicsclassroom.com/mmedia/kinema/avd.cfm

2nd Law: acceleration of an object is proportional to the mass of the object being accelerated

• F=ma – a is in m/s/s – m is in kg, – F is kgxm/s/s or

Newtons

• F = mg (weight)– Gravity (9.8 m/s/s)

http://www.physicsclassroom.com/mmedia/newtlaws/efar.cfm

Unbalanced force

• The normal force is cancelled by the force of gravity.

• The book is sliding to the right but there is no force in that direction.

• Because SLIDING friction is currently the only horizontal force it will cause the book to come to a stop

Sliding Friction

• If a car slams on its brakes and skids to a stop (without antilock brakes), there is a sliding friction force exerted upon the car tires by the roadway surface.

Causes of friction:

• When the high points of each surface touch they bond, you must break these bonds to move one of the pieces (origin of static friction)

• As surfaces move across each other, electrostatic forces continue to attract between high points, resulting in the weaker kinetic friction

• Air drag (any fluid) depends on speed of the motion (getting larger as speed increases)

• size and shape of object• density of fluid

Forces• (Ff) Friction Force: The

contact force that acts to oppose sliding motion between surfaces. Parallel to the surface Opposite the direction of sliding

• Normal force (FN): The contact force exerted by a surface on an object. Perpendicular to and away from the acceleration of the object barring any resistive forces.

3rd law:

• For every action there is an equal and opposite reaction

http://www.physicsclassroom.com/mmedia/momentum/crete.cfm