Rapid Fire AP Physics North Allegheny Sr. High Kernion

1. Rapid Fire AP PhysicsNorth Allegheny Sr. HighKernion (Things you REALLY need to know to get a 5 on the test)

2. 1.Watch for prefix consistencyex: km and cm

3. 2.Transformer Equations • Pprimary = Psecondary • (IV) primary = (IV) secondary • Vs/VP = Ns/NP • IP/Is = Ns/NP

4. Centripetal Force • Never add a force Fc • The centripetal force is the net force acting toward the center of the circular path

5. Rotational/Linear Motion • Every linear equation has a rotational (angular) analog • Ex. ∑F=ma -> ∑T= Iα • Tie in equation: v=r ω

6. Impulse • J=FΔ t • Can be used to find force and then force can be use in FBD • F=ma  F=mΔv/Δt  FΔt = mΔv • Impulse = Change in momentum

7. SHM Equations • X=Acos(wt) • For those who know calc…. • V=dx/dt=-wAsin(wt) • a=dv/dt=-w2Acos(wt)=-w2x • THUS: if x is + the a is – and visa versa • w=(k/m)1/2 • 2πf=w • f=1/T • Be able to interpret these parameters graphically

8. For an Ideal Gas • ΔU=ncvΔT in all processes • R/NA = k (Boltzmann’s constant…1.382E-23)

9. Test Taking Clue • Scan for response types before you begin to solve the problem. • EX: Are the responses numerical or symbolic?

10. Work done by a B-field • WB = 0 ALWAYS • No change in K….and since W=ΔK….

11. Accelerating Voltage • The potential energy gained by a charged particle as it moves across and electric field is determined by the potential difference across the field… • qΔV = ΔU and ΔU = - ΔK

12. Potential Difference • VAB = the potential at A relative to the potential at B. • VAB = VA – VB • V at infinity = 0 by convention • Vpoint particle= kq/r (THIS IS A SCALAR)

13. Equipotentials • Surface on which all points have the same electric potential • The interior of a conductor is equipotential with the value not equal to zero • The potential decreases away from the surface of a conductor with the inverse of the distance v R r

14. Right Hand Rules • Force Rule • Thumb: charge flow direction • Fingers: B-field • Palm: Force of particle • B-field Rule • Curl of fingers: B-field circular lines • Thumb: current direction in the conductor • Current Rule • Curl of fingers: Current in the loop • Thumb: B-field in the plane of the loop

15. Bernoulli’s Equation • The Bernoulli Equation can be considered to be a statement of the conservation of energy principle appropriate for flowing fluids. Note: If the height doesn’t change the pressure must increase if the speed decreases P1 + ½ ρv12 + ρgy1 = P2 + ½ ρv22 + ρgy2 ρ=density v=velocity y = height P=Pressure

16. Total Equilibrium • For a system in complete equilibrium the summation of the forces AND the summation of the torques (about any axis) must be zero • Three equations…three unknowns

17. Torque • Torque = r x F • Torque = rFsinθwith θ = angle between the position vector r and the force vector F • lever arm = l = rsinθ= perpendicular from the line of action of the force to the pivot • Torque = l F Force l pivot

18. Power • Power is the rate at which energy is utilized….P=E/t • This concept shows up in MANY areas of physics • ex: in electrical circuitry P=IV • ex: in mechanics P=W/t • Key units: Watt (J/s) and Kilowatts (1000J/s) • Don’t get confused with the kilowatt-hour, which is a unit of energy (1 KWh=3.6x106 J)

19. Lenz’s Law • An induced current will be produced any time the magnetic flux changes in a loop of wire. The induced current will produce its own B-field to counterbalance the change in flux • Magnetic Flux = Φ = BAcosθ(for uniform B-fields) current N S

20. Basic Mechanics Stuff • Always show the F.O.R. and stick to it • Choose the positive direction for the F.O.R. to be in the direction of the acceleration if a≠0 Be able to determine the tension in the string when object 1 slides across the frictionless table T=(m1m2g)/(m1+m2) 1 2

21. Object tossed into the Air • At the top of the path the velocity is zero but the acceleration is still g path

22. Basic Mechanics Stuff • Normal force can also be called “support force”, “scale reading”, and various other names which refer to the force applied perpendicular to a surface by a surface. • Each friction force has a normal force associated with it…keep the subscripting straight!

23. Planetary Stuff • Kepler’s Laws describe planetary motion • Path is elliptical with the sun at one focus • Equal areas are swept out in equal times, thus the speed of the planet changes • The square of the period of the motion is proportional to the cube of the semimajor axis. In the case of a nearly circular orbit the relationship is T2 is proportional to R3

24. Rotational Kinetic Energy • When an object rolls down a hill, the total amount of K is determined by the following formula: Ktotal = ½ mv2 + ½ Iω2

25. Centripetal Acceleration • When an object is moving in a circular path at a constant speed, its velocity is tangent to the path and continuously changing. Thus it accelerates. The magnitude of the acceleration is: ac = v2/r

26. Relative Velocity in a Boat • When an object is moving relative to a medium which is also moving, the velocity vectors must add together to give the overall velocity relative to some F.O.R. • Ex: vBE = vBW + vWE (Connected H to T) VBW VBE vWE

27. Kinematic Equations • When two objects are moving, you can generate a kinematic equation(s) for each, and then combine them through a common variable such as time or distance.

28. THE MOST IMPORTANT POINTS YOU MUST DECIDE TO FOCUS ON PHYSICS….TO DO OTHERWISE IS TO HAVE WASTED TIME THIS YEAR GET A GOOD NIGHT’S SLEEP THE NIGHT BEFORE THE TEST, EVEN IF YOU LOSE A FEW HOURS OF STUDY TIME RELAX…YOU CAN DO THIS! GOOD LUCK!