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Which formulas in physics describe centripetal acceleration? What are the typical problems? Best be able to give me a few related websites, thank you
a=v^2/r=ω^2*r=(2π/T)^2*r=(2πf)^2*r=v*ω
It is suitable for uniform circular motion in horizontal plane and instantaneous state of variable speed circular motion in vertical plane, etc
There is a 1.2m long lever with 50N weight on the left and 100N weight on the right to balance the lever. How many meters should the fulcrum be away from the right end? If there are 50N objects on both ends, how many meters should the fulcrum move?
There is a 1.2m long lever with 50N weight on the left and 100N weight on the right to balance the lever. How many meters should the fulcrum be away from the right end? If there are 50N objects on both ends, how many meters should the fulcrum move?
Let X be the distance between the fulcrum and the right end
F1*L1=F2*L2
50×(1.2-x)=100×x
x=0.4m
F1'*L1'=F2'*L2'
(50+50)×(1.2-x')=(100+50)×x'
x'=0.48m
X '- x = 0.08m, the fulcrum moves to "left" by 0.48M
The formula of physics problem
54km / h = 15m / s 10m / S = 36km / h 0.5m/s = 1.8km/h 108km / h = 30m / s 300m / min = 5m / s 300m / min = 18km / h
1km / h = 1000 △ (60 × 60) m / S = 1 / 3.6m/s, so 1m / S = 3.6km/h
1m / min = 1 / 60 m / s, so 1m / S = 60 m / min
Find the formula of physical frequency
Junior high school formula: C = in F, wavelength (in), frequency (f) and wave velocity (c) Note: C = 3 * 10 octave M / S
Calculation formula and definition of frequency
In short, it is cycle / time. Definition: the number of cycles in a period of time
A formula for calculating physical heating efficiency
What is the calculation formula of mechanical efficiency of physical internal combustion engine?
η = w / Q = FS / QM
n=W/q=(FS)/QM
Efficiency = active work (mechanical work of automobile w = FS) / total work (total heat released by fuel combustion q = QM)
How many amperes does a 100W 220V lamp pass
P = when UI works normally, I = P / u = 100 / 220 = 0.45a
Physics elective 3-1 all formulas
10、 Electric field
1. Two kinds of charge, charge conservation law, elementary charge: (E = 1.60 × 10-19c); the charge quantity of charged body is equal to the integral multiple of elementary charge
2. Coulomb's Law: F = kq1q2 / R2 (in vacuum) {F: force between point charges (n), K: electrostatic constant, k = 9.0 × 109n &; m2 / C2, Q1, Q2: electric quantity of two point charges (c), R: distance between two point charges (m), direction on their connecting line, force and reaction, mutual repulsion of the same kind of charges, mutual attraction of different kinds of charges}
3. Electric field strength: e = f / Q (definition formula, calculation formula) {e: electric field strength (n / C), is vector (superposition principle of electric field), Q: electric quantity of inspection charge (c)}
4. The electric field formed by the vacuum point (source) charge e = KQ / r2 {R: the distance from the source charge to the position (m), Q: the electric quantity of the source charge}
5. The field strength of uniform electric field E = UAB / D { UAB:AB The voltage (V) between two points, D: the distance (m) of AB two points in the direction of field strength}
6. Electric field force: F = QE {F: electric field force (n), Q: electric quantity of electric charge (c), e: electric field intensity (n / C)}
7. Potential and potential difference: UAB = φ a - φ B, UAB = WAB / Q = - Δ EAB / Q
8. Work done by electric field force: WAB = quab = eqd {WAB: work done by electric field force when charged body is from a to B (J), Q: charge (c), UAB: potential difference between a and B in electric field (V) (work done by electric field force is independent of path), e: intensity of uniform electric field, D: distance between two points along the direction of electric field strength (m)}
9. Electric potential energy: EA = q φ a {EA: electric potential energy of charged body at point a (J), Q: electric quantity (c), φ A: electric potential at point a (V)}
10. Change of electric potential energy Δ EAB = eb-ea {difference of electric potential energy of charged body from position a to position B in high school physical circuit experiment in electric field}
11. Work done by electric field force and change of electric potential energy Δ EAB = - WAB = - quab (the increment of electric potential energy is equal to the negative value of work done by electric field force)
12. Capacitance C = q / u (definition formula, calculation formula) {C: capacitance (f), Q: electric quantity (c), u: voltage (potential difference between two plates) (V)}
13. Capacitance of parallel plate capacitor C = ε s / 4 π KD (s: opposite area of two plates, D: vertical distance between two plates, ω: dielectric constant)
Common capacitors
14. Acceleration of charged particles in electric field (VO = 0): w = Δ EK or Qu = mvt2 / 2, VT = (2qu / M) 1 / 2
15. Deflection of charged particles in the direction perpendicular to the electric field at the velocity VO into the uniform electric field (without considering the effect of gravity)
Quasi plane vertical electric field direction: uniform linear motion L = VOT (in parallel plates with equal amount of heterogeneous charges: e = u / D)
The throwing motion is parallel to the electric field direction: the uniformly accelerated linear motion with zero initial velocity d = at2 / 2, a = f / M = QE / m
Note: (1) when two identical charged metal balls are in contact, the distribution law of electric quantity is as follows: those with different charges are neutralized first and then equally divided, and those with same charges are equally divided;
(2) the electric field line starts from the positive charge and ends at the negative charge. The electric field line does not intersect, and the tangent direction is the direction of field strength. The electric field is strong at the close position of the electric field line, and the electric potential is lower and lower along the electric field line, and the electric field line is perpendicular to the equipotential line;
(3) summarize the common high school physics knowledge points of electric field, and memorize the distribution of electric field lines;
(4) the electric field strength (vector) and electric potential (scalar) are determined by the electric field itself, and the electric field force and electric potential energy are also related to the amount of electric charge and the positive and negative charge of the charged body;
(5) in electrostatic equilibrium, the conductor is an equipotential body, and the surface is an equipotential surface. The electric field line near the outer surface of the conductor is perpendicular to the surface of the conductor, and the combined electric field strength inside the conductor is zero. There is no net charge inside the conductor, and the net charge only distributes on the outer surface of the conductor;
(6) capacitance unit conversion: 1F = 106 μ f = 1012pf;
(7) EV is the unit of energy, 1eV = 1.60 × 10-19j;
(8) other related contents: electrostatic shielding, oscillograph, oscilloscope and its application, equipotential surface
Xi. Constant current
1. Current intensity: I = q / T {I: current intensity (a), Q: electric quantity (c), t: time (s)}
2. Ohm's Law: I = u / R {I: current intensity of conductor (a), u: voltage at both ends of conductor (V), R: resistance of conductor (Ω)}
3. Resistance and resistance law: r = ρ L / s {ρ: resistivity (Ω & # 8226; m), l: conductor length (m), s: conductor cross-sectional area (M2)}
4. Ohm's law of closed circuit: I = E / (r r) or E = IR, IR can also be e = u inside u outside
{I: total current in the circuit (a), e: power supply electromotive force (V), R: external circuit resistance (Ω), R: power supply internal resistance (Ω)}
5. Electric work and electric power: w = uit, P = UI {W: electric work (J), u: voltage (V), I: current (a), t: time (s), P: electric power (W)}
6. Joule's Law: q = i2rt {Q: Electrothermal (J), I: current through conductor (a), R: electrical resistance of conductor (Ω), t: power on time (s)}
7. In pure resistance circuit: because I = u / R, w = q, because of the three, w = q = uit = i2rt = u2t / R
8. Total power rate, power output power and power efficiency: P total = ie, P output = IU, η = P output / P total {I: total circuit current (a), e: power electromotive force (V), u: terminal voltage (V), η: power efficiency}
9. Series / parallel series circuit (P, u and R are proportional) and parallel circuit (P, I and R are inverse)
Resistance relation (series parallel reverse) R series = R1 R2 R3 1 / R parallel = 1 / R1 1 / r2 1 / R3
Current relation I total = I1 = I2 = I3 I and = I1 I2 i3
Voltage relation u total = U1 U2 U3 u total = U1 = U2 = u3
Power distribution P total = P1 P2 P3 P total = P1 P2 P3
10. Measure resistance with ohmmeter
(1) circuit composition (2) measurement principle
After the two probes are short circuited, adjust RO to make the pointer of the meter fully deviate
Ig＝E/(r Rg Ro)
After connecting to the measured resistance Rx, the current passing through the meter is
IX = E / (r RG ro Rx) = E / (r in Rx)
Because IX corresponds to Rx, it can indicate the measured resistance
(3) usage: mechanical zero adjustment, range selection, Ohm zero adjustment, measurement reading {pay attention to gear (magnification)}, shift off gear
11. Measuring resistance by voltammetry
Ammeter internal connection method:
Voltage representation: u = ur UA
Ammeter external connection method:
Current representation: I = IR IV
The measured value of Rx = u / I = (UA ur) / IR = RA RX > r true
The measured value of Rx = u / I = ur / (IR IV) = rvrx / (RV R) > RA [or RX > (rarv) 1 / 2]
Select circuit condition RX
According to the book
Seeking 3-1 formula of physics elective course
My is the Shandong version of
All the formulas... I just want the formula
The most important ones are:
R=p*l/s
I=q/t=nesv
C=Q/U C=&S/4(3.14)kd
P total = P output + P internal (engine calculation)
E = u + IR
The use of ohmmeter, (steps, reading method) - experimental problems
Using Peian method to measure resistance, paying attention to the internal and external connection of ammeter, partial voltage method and current limiting method
Magnetic field and electric field
f=qvB=mv2/R
F = EQ, e = KQ / R (for point charge in vacuum)
U = w / q u = ed
W = QED (for uniform electric field)
How specific? Do you need to explain every formula?
f=kQq/r^2 k=9*10^9
F = EQ, e = KQ / R (for point charge in vacuum)
U=W/q U=Ed
C=Q/U C=&S/4(3.14)kd
I=q/t=U/R
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