………………………………………………………………………………
………………………………………………………………………………
Physical quantity unit formula
Name symbol name symbol
Mass m kg kg
Temperature t centigrade℃ m=pv
Speed v m/sec m/sec v = sec/sec
Density rho kg/m? 0? 6 kg/m？ 0? 6 ρ=m/v
Force (gravity) f Newton (cattle) N G=mg
Pressure p Pascal (Pa) Pa P=F/S
Work w joule (coke) J W=Fs
Power p watt (watt) w P=W/t
Current I Ampere (A) A I = U/R.
Voltage u volts (volts) V U=IR.
Resistance r ohm (ohm) ω r = u/i.
Electric power watt Joule (joule) watt =UIt
Electric power p watt (W) w P=W/t=UI.
Heat q joule (coke) J Q = cm (t-t0)
Specific heat C Jiao/(kg Celsius) J/ (kg Celsius)
………………………………………………………………………………
………………………………………………………………………………
Summary of junior high school physics formula
Summary of junior high school physics formula
It seems to be from high school. There will be one in junior high school, but not many.
Deformation of Remarks Formula of Physical Quantity (Unit) Formula
Velocity v
(m/s) v=
Student: Distance
T: time
Gravity g
(N) G=mg m: mass.
G: 9.8n/kg or 10N/kg.
Density ρ
(kg/m3) ρ =
M: quality
Five: volume
He Lihe
(n) Same direction: F =F 1+F2.
Opposite direction: F =F 1-F2 When the direction is opposite, f1> Second generation
Buoyancy f float
(N) F float =G object -G sight G sight: the gravity of an object in a liquid.
Buoyancy f float
(n) The formula f float = g object is only applicable.
Objects float or suspend.
Buoyancy f float
(n) f float = g row = m row g = ρ liquid gv row: the gravity of the liquid shifts.
Line m: mass of displacement liquid.
ρ liquid: density of liquid
The fifth line: the volume of liquid discharged.
(i.e. the volume immersed in liquid)
Lever balance condition f1L 1 = f2l2f1:power l1:power arm.
F2: resistance L2: resistance arm
Crown block F=G object
S=h F: tension at the free end of the rope.
G object: the gravity of the object.
S: the distance that the free end of the rope moves.
H: the rising distance of the object.
Moving pulley F= (G object +G wheel)
S=2 h G object: the gravity of the object
G wheel: the gravity of the moving pulley.
Pulley block F= (G object +G wheel)
S=n h n: the number of rope segments passing through the moving pulley.
Mechanical work w
(J) W=Fs F: force
S: distance moved in the direction of force.
effective work
Total work w total w has =G substance h
W total =Fs is suitable for the case that the pulley block is placed vertically.
Mechanical efficiency η= × 100%
Power supply p
(w) P=
Woman: Work.
T: time
Pressure p
(Pa) P=
pressure
stressed zone
Liquid pressure p
(pa) p = rhogh rho: liquid density.
H: depth (from liquid level to required point)
Vertical distance)
Heat q
(J) Q=cm△t c: specific heat capacity m: mass.
△t: change value of temperature
Fuel combustion emission
Q(J) Q=mq m: quality
Q: calorific value
Common physical formulas and important knowledge points
I. Physical formula
Deformation of Remarks Formula of Physical Quantity (Unit) Formula
series circuit
Current I (a) I = I 1 = I2 = ... Current is equal everywhere.
series circuit
The voltage u (v) u = u 1+U2+ ... from the series circuit.
Partial pressure action
series circuit
The resistance r (ω) r = r 1+R2+ ...
parallel circuit
Current I (a) I = i 1+I2+ ... The main currents are equal.
Sum of branch currents (shunt)
parallel circuit
Voltage u (v) u = u 1 = U2 = ...
parallel circuit
Resistance r (ω) =++ ...
Ohm's law I=
Current and voltage in the circuit
Directly and inversely proportional to the resistance.
Current definition I=
Q: Charge (Coulomb)
time
Electrical engineering w
(J) W=UIt=Pt U: Voltage I: Current
T: time p: electricity
Electric power P=UI=I2R=U2/R U: voltage I: current.
R: resistance
Electromagnetic wave velocity and wave
The relationship between length and frequency C=λν C: wave velocity (the wave velocity of electromagnetic wave is constant, equal to 3× 108m/s).
λ: wavelength v: frequency
2. Knowledge points
1. Several values to remember:
A. the speed of sound in air: 340m/s b the speed of light in vacuum or air: 3x108m/s/s.
C density of water: 1.0× 103kg/m3 d specific heat capacity of water: 4.2× 103J/(kg? 6? 1℃)
E. dry battery voltage:1.5v f. household circuit voltage: 220V.
G. safe voltage: not higher than 36V.
2. Density, specific heat capacity and calorific value are the characteristics of substances, and the values of these three physical quantities of the same substance are generally unchanged. For example, a glass of water and a bucket of water have the same density and specific heat capacity.
3. A virtual image of the same size formed by a plane mirror, in which the image and the object are symmetrical about the plane mirror.
Sound cannot travel in a vacuum, but light can travel in a vacuum.
4. Ultrasonic waves: sounds with frequencies higher than 2000, such as bats and ultrasonic radar;
Infrasound: Volcanic eruption, earthquake, wind explosion and tsunami will all produce infrasound, and nuclear explosion and missile launch will also produce infrasound.
6. Light travels in a straight line in the same homogeneous medium. Shadow, pinhole imaging, solar eclipse and lunar eclipse are all formed by light propagating along a straight line.
7. When light is refracted, the angle in the air is always slightly larger. Looking at the things in the water, I see a shallow virtual image.
8. Convex lens converges light and concave lens diverges light.
9. The law of convex lens imaging: the object becomes a reduced and inverted real image outside the focal length of 2 times. Between 2 times the focal length and 1 times the focal length, it is an inverted magnified real image. In the focal length of 1 times, it becomes a vertical magnified virtual image.
10. Sliding friction is related to pressure and surface roughness. Rolling friction is smaller than sliding friction.
1 1. Pressure is a physical quantity that compares the effect of pressure, and the effect of pressure is related to the size of pressure and the stress area.
12. When transmitting voltage, high voltage transmission should be adopted. The reason is that the power loss on the transmission line can be reduced.
13. The principle of the motor: the electrified coil is forced to rotate in the magnetic field. It is the conversion from electric energy to mechanical energy.
14. Generator principle: electromagnetic induction phenomenon. Mechanical energy is converted into electrical energy. Microphones and transformers are based on the principle of electromagnetic induction.
15. Optical fiber is the medium for transmitting light.
16. The magnetic induction line emanates from the N pole of the magnet and finally returns to the S pole.
Note: When there is voltage and electric power on the nameplate, calculate R first, (R=) In addition, if there is "normal operation" in the title, it implies the conditions.
Due to the limited space, some knowledge points are listed, and the rest are all done by myself.
Units and formulas of physical quantities
………………………………………………………………………………
Physical quantity unit formula
Name symbol name symbol
Mass m kg kg m=ρv
Temperature t centigrade℃
Speed v m/sec m/sec v = sec/sec
Density ρ kg/m 3 kg/m3 ρ=m/v
Kg/m3 3 kg/m3
Force (gravity) f Newton (cattle) N G=mg
Pressure p Pascal (Pa) Pa P=F/S
Work w joule (coke) J W=Fs
Power p watt (watt) w P=W/t
Current I Ampere (A) A I = U/R.
Voltage u volts (volts) V U=IR.
Resistance r ohm (ohm) ω r = u/i.
Electric power watt Joule (joule) watt =UIt
Electric power p watt (W) w P=W/t=UI.
Heat q joule (coke) J Q = cm (t-t0)
Specific heat C Jiao/(kg Celsius) J/ (kg Celsius)
The speed of light in vacuum is 3x108m/s.
9.8 N/kg
15 C the speed of sound in the air is 340 m/s.
Safe voltage is not higher than 36 volts.
1, liquid pressure p = GH2. Archimedes principle F float = G drain = gV drain3. Lever balance
Conditions: f1l1= f2l2; 4. Mechanical efficiency = ×100%; 5. Joule's Law: Q = I2RT
(q = w)； if the circuit is a pure resistance circuit); 6. If you know the rated voltage U and rating of an electrical appliance.
Power p, and the actual voltage u is a real number, then the resistance of the electrical appliance during normal operation is r = p Real number = =( )2P.
; 7. Power p = Fv8. Characteristics of series circuit: I = I1= I2; u = u 1+U2； r = r 1+R2；
. Characteristics of parallel circuit: I = I1+I2; U 1=U2=U
force
Line m: mass of displacement liquid.
ρ liquid: density of liquid
The fifth line: the volume of liquid discharged.
(i.e. the volume immersed in liquid)
Lever balance condition f1L 1 = f2l2f1:power l1:power arm.
F2: resistance L2: resistance arm
Crown block F=G object
S=h F: tension at the free end of the rope.
G object: the gravity of the object.
S: the distance that the free end of the rope moves.
H: the rising distance of the object.
Moving pulley F= (G object +G wheel)
S=2 h G object: the gravity of the object
G wheel: the gravity of the moving pulley.
Pulley block F= (G object +G wheel)
S=n h n: the number of rope segments passing through the moving pulley.
Mechanical work w
(J) W=Fs F: force
S: distance moved in the direction of force.
effective work
Total work w total w has =G substance h
W total =Fs is suitable for the case that the pulley block is placed vertically.
Mechanical efficiency η= × 100%
Power supply p
(w) P=
Woman: Work.
T: time
Pressure p
(Pa) P=
pressure
stressed zone
Liquid pressure p
(pa) p = rhogh rho: liquid density.
H: depth (from liquid level to required point)
Vertical distance)
Heat q
(J) Q=cm△t c: specific heat capacity m: mass.
△t: change value of temperature
Fuel combustion emission
Q(J) Q=mq m: quality
Q: calorific value
Common physical formulas and important knowledge points
I. Physical formula
Deformation of Remarks Formula of Physical Quantity (Unit) Formula
series circuit
Current I (a) I = I 1 = I2 = ... Current is equal everywhere.
series circuit
The voltage u (v) u = u 1+U2+ ... from the series circuit.
Partial pressure action
series circuit
The resistance r (ω) r = r 1+R2+ ...
parallel circuit
Current I (a) I = i 1+I2+ ... The main currents are equal.
Sum of branch currents (shunt)
parallel circuit
Voltage u (v) u = u 1 = U2 = ...
parallel circuit
Resistance r (ω) =++ ...
Ohm's law I=
Current and voltage in the circuit
Directly and inversely proportional to the resistance.
Current definition I=
Q: Charge (Coulomb)
time
Electrical engineering w
(J) W=UIt=Pt U: Voltage I: Current
T: time p: electricity
Electric power P=UI=I2R=U2/R U: voltage I: current.
R: resistance
Electromagnetic wave velocity and wave
The relationship between length and frequency C=λν C: wave velocity (the wave velocity of electromagnetic wave is constant, equal to 3× 108m/s).
λ: wavelength v: frequency
2. Knowledge points
1. Several values to remember:
A. the speed of sound in air: 340m/s b the speed of light in vacuum or air: 3x108m/s/s.
C density of water: 1.0× 103kg/m3 d specific heat capacity of water: 4.2× 103J/(kg? ℃)
E. dry battery voltage:1.5v f. household circuit voltage: 220V.
G. safe voltage: not higher than 36V.
2. Density, specific heat capacity and calorific value are the characteristics of substances, and the values of these three physical quantities of the same substance are generally unchanged. For example, a glass of water and a bucket of water have the same density and specific heat capacity.
3. A virtual image of the same size formed by a plane mirror, in which the image and the object are symmetrical about the plane mirror.
Sound cannot travel in a vacuum, but light can travel in a vacuum.
4. Ultrasonic waves: sounds with frequencies higher than 2000, such as bats and ultrasonic radar;
Infrasound: Volcanic eruption, earthquake, wind explosion and tsunami will all produce infrasound, and nuclear explosion and missile launch will also produce infrasound.
6. Light travels in a straight line in the same homogeneous medium. Shadow, pinhole imaging, solar eclipse and lunar eclipse are all formed by light propagating along a straight line.
7. When light is refracted, the angle in the air is always slightly larger. Looking at the things in the water, I see a shallow virtual image.
8. Convex lens converges light and concave lens diverges light.
9. The law of convex lens imaging: the object becomes a reduced and inverted real image outside the focal length of 2 times. Between 2 times the focal length and 1 times the focal length, it is an inverted magnified real image. In the focal length range of 1 times, it becomes an upright magnified virtual image.
10. Sliding friction is related to pressure and surface roughness. Rolling friction is smaller than sliding friction.
1 1. Pressure is a physical quantity that compares the effect of pressure, and the effect of pressure is related to the size of pressure and the stress area.
12. When transmitting voltage, high voltage transmission should be adopted. The reason is that the power loss on the transmission line can be reduced.
13. The principle of the motor: the electrified coil is forced to rotate in the magnetic field. It is the conversion from electric energy to mechanical energy.
14. Generator principle: electromagnetic induction phenomenon. Mechanical energy is converted into electrical energy. Microphones and transformers are based on the principle of electromagnetic induction.
15. Optical fiber is the medium for transmitting light.
16. The magnetic induction line emanates from the N pole of the magnet and finally returns to the S pole.
Note: When there is voltage and electric power on the nameplate, calculate R first, (R=) In addition, if there is "normal operation" in the title, it implies the conditions.