Physical Science Final Exam Review Miss Glover
Motion • Distance in meters: How far you have traveled • Velocity in m/s: How fast you are going • Acceleration in m/s2: Rate of change of velocity- speeding up, slowing down or turning! Equations: Constant V Acceleration Graphs: d d t t
Example: • A truck drives 1000 km in 10 hours, what is it’s speed? • d=1000km t=10 hours v=? v=d/t=1000/10= 100km/hr • A boat travels for 5 hours at 20 miles per hour, How far does it go? • t=5 hr v=20mi/hr d=? d=v(t)=20(5)= 100 mi
Acceleration • A PR runner accelerates from rest to 10 m/s in 4 seconds, what is her acceleration? • Vi=0m/s Vf=10 m/s, t=4 sec a=? • A=(Vf-Vi)/t= (10-0)/4= 2.5 m/s/s
Freefall • ALL objects accelerate towards the Earth at g=10 m/s2 due to the large mass of the Earth • An object that is accelerating is increasing velocity at 10 m/s each second downwards, or decreasing the velocity by 10 m/s each second as it goes upwards. • The distance an object goes while accelerating increases proportional to the time squared. • EQ:
Projectiles • Combine a constant velocity problem horizontally, and a free fall acceleration problem vertically (g=10!). • A ball dropped will hit the ground at the same time as a ball given an initial velocity horizontally. • The only force acting on a projectile is gravity! • Horizontal Angle
Forces- Newton’s Laws • 1st Law: Inertia: An object in motion stays in motion, and an object at rest stays at rest, UNLESS acted upon by an outside net force. • 2nd Law: F=ma: A net force causes a mass to accelerate. • 3rd Law: Action/Reaction: For every force there is an equal and opposite reaction force. EQ:
Forces • Units of force are Newtons= kg (m/s2) Defined as a push or a pull Some forces we have considered: • Force of Gravity (Weight) Fg=m(g)= m(10) m= mass in kg • Force of Friction: A force OPPOSING the motion of two surfaces over each other. Always in the direction opposite the motion. Can be helpful- like providing traction to a car or Can be a hindrance-may cause your brakes to heat up
Energy • Units of Joules • Potential Energy is energy stored up due to an objects location in the gravitational field (a height off the ground!) • Kinetic Energy is energy due to an object’s motion. • If energy is conserved, the energy at the PE at the top of a tree or coaster will equal the KE at the bottom.
Work and Power • You give objects energy (PE or KE) by doing WORK! • To do work you apply a force over a distance. • Work will equal the energy you gain, so it also has units of Joules. • Power is the rate of doing work or the Work/Time
Work Example • A force of 20 N is applied to a box to move it a distance of 8 m, how much work is done? • F=20 N, d=8m, W=? • W=F(d)= 20(8)= 160 J
Simple Machines • Used to reduce or change the direction of a force needed to do work by increasing the distance over which the force is applied. • Seven Types: Lever, Pulley, Inclined Plane, Gear, Wheel and Axle, Wedge, Screw • Simple machines involved just one motion- ramp, door knob, handle etc… two or more simple machines may be combined to make a complex machine like a wheel barrel or a bike!
Simple Machine Calculations • The ratio of the force you get from a machine compared to the force you need to apply is called the Mechanical Advantage (MA). • The ratio of the distance you must apply the force compared to the distance the machine applies the force is called the Ideal Mechanical Advantage (IMA)
Simple Machines Examples • A lever is used to lift a 10,000 lb car with a force of 500 lbs, what is the mechanical advantage of the lever? • Fe=500 lbs, Fr=10,000 lb MA=Fr/Fe • MA= 10000/500 =20 (no units!) • A inclined plane is 10 feet long and 2 feet tall, what is the Ideal Mechanical Advantage? • de=10ft, dr=2 ft, IMA=de/dr • IMA=10/2=5 (mo units!)
Momentum • A object that is moving has momentum! • Momentum (p)= mass (velocity) units: kg(m/s) • The more mass or velocity an object has, the more momentum it has. • For a given mass, the faster moving object will have more momentum. • Force a given velocity, the more massive object will have more momentum.
Momentum Examples • Which has more momentum, a 2000 kg car moving at 1 m/s, or a 1 kg mass moving at 2000 m/s? • p=m(v) so they have the SAME momentum! • Joe with a mass of 75 kg, runs at 2 m/s during warm-ups and 10 m/s during the race, when does he have more momentum? • p= m(v) so more velocity, more momentum!
Momentum and Impulse • To change an object’s momentum you could change its mass or velocity. This can be done by altering the object or applying a force! • Applying a force over a time is called an Impulse and it will equal the change in momentum. • Egg drop/Air bags: Extend the time, reduce the force • Follow through: Extend the time to increase the change in momentum.
Waves • All waves transport energy through the medium. • The medium is the material that the wave is passed on through- water, air, glass… • The wave speed will depend on what medium your are traveling through and equals frequency times wavelength
Types of Waves • Transverse Waves- Particles move perpendicular to the wave motion. EX: Coil, slinky, guitar string • Longitudinal Waves- Particles move parallel to the wave motion. EX: Sound, Grab and release slinky coils. • Transverse and longitudinal NEED a medium! • Electromagnetic Waves- DO NOT need a medium to be passed on- can travel in a vacuum (empty space)
Parts of a Wave Crests: Top of wave Troughs: Bottom of Waves Wavelength: Distance for one full wave- Crest to Crest (A-E) or (E-H)(l) Compression: High Pressure Region Rarefaction: Low Pressure Region
Wave Behaviors • Reflection- bouncing of a wave off of a barrier • Refraction-Change in wave speed due to a change in medium • Diffraction- Bending of a wave around a barrier • Interference- Two or more waves going through he same medium at the same time.
Sound • Sound travels fastest in a solid, slowest in cold air • The speed of sound depends on the temperature of the air • The highness or lowness is the PITCH of a sound • The volume of sound is determine by its intensity
Electromagnetic Waves • All electromagnetic waves travel at c=3 X 108 m/s • Exhibit all wave behaviours Low frequency High frequency
Lenses and Mirrors • Lenses Refract Light, Mirrors Reflect Light • Real- Light rays actually cross (can focus on screen) • Virtual- Light rays only appear to cross (cannot focus on a screen) • Erect- Right side up • Inverted- Upside down • Larger/Smaller- Image size compared to object
Lenses and Mirrors • Converging: Convex Lens/Concave Mirror • Inside the focal point: Larger, Erect, Virtual • Outside the focal point: Inverted, Real • Examples: Magnifying glass, telescope, make up mirror, glasses • Diverging: Concave Lens/Convex Mirror • ALWAYS Smaller, erect, virtual • Examples: Security mirror, glasses
Ray Diagrams • In parallel, out through the focus • In through the focus, out parallel • Draw an image where the rays meet, or appear to meet. • Describe the image as Real or Virtual Erect or Inverted Larger or Smaller