Physics Topics 1. Motion 2. Measuring Matter 3. Work, Power, Machines 4. Newton’s Laws 5. Waves 6. Momentum 7. Pressure

Acceleration is the rate of change in the speed of an object.

 Positive acceleration and positive speed

 Negative acceleration and positive speed

Change in speed (m/sec) Change in time (sec) Acceleration (m/sec 2 ) =

 A student conducts an  acceleration experiment by coasting a bicycle down a steep hill.  The student records the speed of the bicycle every second for five seconds.  Calculate the acceleration of the bicycle.

 Constant acceleration is different from constant speed.  Motion with zero acceleration appears as a straight horizontal line on a speed versus time graph. zero acceleration constant speed

 Constant acceleration is sometimes called uniform acceleration.  A ball rolling down a straight ramp has constant acceleration. constant acceleration increasing speed

 An object can have acceleration, but no speed.  Consider a ball rolling up a ramp.  As the ball slows down, eventually its speed becomes zero. constant negative acceleration decreasing speed

MASS, VOLUME, & DENSITY

 Definition: Amount of matter in an object  Units: kg or g  Mass is different from weight because…Weight depends on pull of gravity

 Definition: How much space an object takes up  Regular shaped object (box) then V= L x W x H (cm 3 or m 3 )  Liquids - to find volume…use graduated cylinder (mL or L)  Use graduated cylinder for odd shaped solid objects (cm 3 or m 3 )

 Obtain a clean graduated cylinder.  Fill the graduated cylinder with enough water to cover object. Record the volume  Carefully place the object into the water filled graduated cylinder.  Record the new water level.  The volume of the object is the V final – V initial

 Density is the measurement of the mass of an object per unit volume of that object.  Formula: D (density) = m (mass) V(volume)

 A rock has a mass of 25.7 grams and a volume of 3.56 cm 3. Find the density.  1st write: D = mass volume  2nd: Substitute in the measurements D = 25.6 g 3.56 cm 3  3rd: Calculate following sig fig rules. Density = 7.19 g/ cm 3

 Calculate the density of a marble that has a mass of 13.6 grams and a volume of 6.1 cm 3.  D = m/V = 13.6 g / 6.1 cm 3  D = m/V = 2.2 g / cm 3

 If you pack more mass into the same volume, it is more dense.  Example: packing wet sand into a bucket

 If you pack the SAME mass into a SMALLER volume, it is MORE dense  Example: a trash compactor.

 Just because something has more mass DOES NOT mean it is more DENSE.

Distance 10 m Force 40 N W = F * d = 40 N * 10 m = 400 Joules Force acting through a distance

 Force must be in same direction as distance Force Distance

% Efficiency = Work Output / Work Input *100 Work InputWork Output F effort *distanceF resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m = 50J20N*2m = 40J

% Efficiency = (40 J / 50 J) = 0.8 Work InputWork Output F effort *distance F resistance *distance Work Input is always greater than Work Output due to Friction 10N*5m = 50J 20N*2m = 40J

 I. Law of Inertia  II. F = ma  III. Action / Reaction <>

A force is… a push or a pull. Friction, Drag, Gravity, and Weight are forces…

Law I: Inertia vs. Mass Bigger masses have more… Smaller masses have less inertia. But inertia does not equal mass.

F = ma Force equals mass x acceleration Newton’s 2nd Law:

F = ma mass = 10 kg acceleration = 2 m/s Find the Force. F = 10 kg x 2 m/s = 20 N 2 2

Action Reaction Newton’s 3rd Law:

You exert force on the weights and… The weights exert the same force on you.

Water is pushed back and… the boat is pushed forward.

Physics FCAT Dr. Persin

What are waves?

36 a wave is a disturbance that travels away from a source.

37  sound waves  visible light waves  radio waves  microwaves  water waves  sine waves  telephone chord waves  stadium waves  earthquake waves  waves on a string  slinky waves

38  Waves transfer energy with transferring matter.  Lets do a Stadium Wave!

 A wave transfers energy from place to place.  What carries waves?  A medium, a medium is the material through which a wave travels.  A medium can be a gas, liquid, or solid.

 Waves are created when a source of energy causes a medium to vibrate.  A vibration is a repeated back and forth or up and down motion.

v = velocity f = frequency  = wavelength

v = velocity, m/s f = frequency, Hertz (Hz) λ = wavelength, m λ is the Greek letter “lambda”

 Calculate the velocity of a wave with a frequency of 250 Hz and a wavelength of 3 m.  v = f = 250 Hz  3 m  v = 750 m/s

What is momentum? All objects have mass. So if an object is moving, then it has momentum. It is mass in motion. Momentum = mass * velocity Equation: p = m V

Determine the momentum of a... a. 60 kg body moving at 9 m/s. b kg car moving at 20 m/s. c. 40 kg freshman moving at 2 m/s Answers: a. 540 kg m/s b. 20,000 kg m/s c. 80 kg m/s

 Conceptual Check: If the boulder and the boy have the same momentum, will the boulder crush the boy? Hint: Which would have the larger speed?

Which has a greater momentum, a skateboard moving at 3 m/s or a stationary ten-wheeler truck ? Explain your answer. When can a ball have the same momentum as an airplane parked on a runway? Explain your answer.  Conceptual Check:

Momentum Rocket = Momentum Exhaust A 20 kg rocket zooms upward at 5 meter/second. At the same exact time, 10 kg of water shoots downward. How fast does the water shoot out?

Here is an example.

FCAT Physics: Part III. Pressure A woman’s high heels sink into the soft ground, but the larger shoes of the much bigger man do not. Why? More Pressure. Pressure = Force / Area

 Calculate the pressure exerted by a heel of a shoe with an area of.02 m 2 if the force of the heel is 50 N.  P = F / A = 50 N /.02 m 2  P = 2500 N / m 2

More nails means less pressure from each one. Get the point! The End.