physics flashcards 1
kinematics equations
vf2=vi2+2ax x=vit+½at2 v=vo+at vavg=(vo+v)/2 x=vt=((vo+v)/2)*t
Newton’s Laws
1st: Law of inertia - objects in motion (or at rest) will stay in motion (or at rest) unless acted on by a nonzero net force 2nd: F=ma 3rd: Fa=-Fb Every action has an equal and opposite reaction
Friction equations
force of friction opposes motion kinetic: ff=μkFN static fs<μsFN
Gravitation
two masses will exert an attractive force on one another inversely proportional to the square of the distance b/w them. F=(Gm1m2)/r2
mnemonic for trig values
sin0=√0/2=0 sin30=√1/2=½ sin45=√2/2 sin60=√3/2 sin90=√4/2=1 cos0=√4/2=1 cos30=√3/2 cos45=√2/2 cos60=√1/2=½ cos90=√0/2=0
centripetal motion
net force on an object at a constant speed on a circular path points toward center of circle Fc=(mv2)/r ac=v2/r
torque
always greatest at 90o to object trying to move τ=rFsinΘ units: N*m
Work
W=FdcosΘ units: N*m=Joules
Kinetic energy
KE=½mv2 units: J
Work energy theorem
Wnet=∆KE and W=∆PE
Gravitational potential energy
U=mgh units: J
Average Power
P=W/t = ∆E/∆t units: Watts
momentum
p=mv
types of collisions
elastic collisions: KE and momentum conserved inelastic collisions: KE not conserved, momentum conserved totally inelastic collisions: KE not conserved, momentum conserved
Impulse
force applied to an object over time I=∆p=Fav∆t units: N*s
Hooke’s Law
F=-kx x=displacement of spring from unstrained length k=proportionality constant units: N/m - = restoring force always opposite to displacement of spring amplitude is max displacement from equilibrium
period in SHM
time required to complete one cycle
angular frequency
ω=2π/t = 2πf=√(k/m) frequency at which object at mass m vibrates on a string units: radians
frequency
f=1/T units: Hz = 1/s the number of cycles of motion per second
Elastic Potential energy
-energy a spring has because of being stretched or compressed. -at max displacement from equilibrium, potential energy of spring is at max and KE is 0 PEelastic=½ kx2 units: J = kg*m2/s2
Total mechanical energy
½mv2+mgh+½kx2
angular frequency of pendulum
ω=2πf=√(g/L) L=length (m)
restoring force of pendulum
F=-mgsin
properties of electromagnetic waves
-transverse, can trave through vacuum -all move through vacuum at speed of light (c)=3.0*108 m/s
speed of electromagnetic waves
v=fλ
λ=wavelength (m)
Electromagnetic spectrum
longest wavelength, lowest frequency and energy:
radio waves, microwaves, infrared, visible (red (700 nm) -violet (400 nm)), ultra-violet, xrays, gamma rays -
shortest wavelength, highest frequency, highest energy
transverse vs. longitudinal waves
material transmitting the wave…
longitudinal - particles are parallel to the direction of motion (think slinky)
transverse - particles are perpendicular to the direction of motion (piece of string moving).
interference
- 2 waves of same frequency have different “phases” - one complete cycle = 360 or 21 radians - in phase if crest of one wave coincides with crest of the other - 90i out of phase - wave is ¼ wavelength ahead of other - 180i out of phase - wave is ¼ wavelength ahead of other
speed of a wave
v=f(lambda)=(angular frequency)/k=(lambda)/T
k=2π/(lambda) –> wavenumber
angular frequency =2πf=2π/T
constructive interference
2 crests of waves in phase meet at same point in space and the amplitude of the resulting wave is the sum of individual amplitudes
destructive interference
a crest and trough meet at the same point in space; amplittude of the resulting wave is difference of individual amplitudes - complete destructive when amplitudes are equal and 180 out of phase
charged particles
exert a force on one another. unlike charges attract, like charges repel
Coulomb’s Law
The electric force that charged objects exert on each other is called the electrostatic force. this depends on the amt. of charge and the distance between objects. the greater the chargers and the closer they are, the greater the force. Fe=k((q1q2)/r2) k=9*109 N*m2/C2 q1 and q2 = charges (C)
Electric Field
E=F/q0 units: N/C - the E at a point is the electrostatic force (F) experienced by a small test charge placed at that point divided by the charge itself - E is a vector, direction is the same as the direction of the force F on a positive test charge. opposite directions if negative test charge
Electric field produced around a point charge q
E=kq/r2 electric field lines point in direction positive charge would move pos - move away from neg - move towards