How many forces do physical formulas calculate
1. Gravity g = mg
(vertically downward, g = 9.8m/s2 ≈ 10m / S2, the action point is at the center of gravity, applicable to the earth surface)
2. Hooke's law f = KX
{along the recovery deformation direction, K: stiffness coefficient (n / M), X: deformation variable (m)}
3. Sliding friction force F = μ FN
{opposite to the relative motion direction of the object, μ: Friction coefficient, FN: positive pressure (n)}
{rrrrrrr}
extended data:
different classification of force
1. According to the nature of force, it can be divided into gravity, universal gravitation, elastic force, friction force, molecular force, electromagnetic force, nuclear force, etc Note that gravity is not equal to gravity under all conditions Gravity does not point to the center of the earth under all conditions. Gravity is a component of the earth's gravitational force on an object, and the other component is a centripetal force. Only on the equator does gravity point to the center of the earth.)
According to the effect of force, it can be divided into tension, tension, pressure, supporting force, power, resistance, centripetal force, restoring force, etc According to the research object, it can be divided into external force and internal force According to the action mode of force, it can be divided into non-contact force (such as gravitation, electromagnetic force, etc.) and contact force (such as elastic force, friction force, etc.) There are four basic interactions (forces): gravitational interaction, electromagnetic interaction, strong interaction and weak interactionnature of force:
materiality: force is the effect of an object (matter, mass) on an object (matter, mass). When an object is subjected to a force, another object must exert this effect on it. Force cannot exist independently without an object
interactivity (interaction): the interaction between any two objects is always mutual, and the object exerting the force must also be the object under the force. As long as one body exerts a force on another, the stressed body in turn will surely add a force to the exerted body Generating conditions: the force is equal in size (the resultant force is zero, in a state of non directional static motion) or not equal, in the opposite direction, acting on two different objects, and acting on the same straight line. It can be summarized as: foreign body, equivalent, reverse, collinear. A pair of interaction forces must proce and disappear at the same time.)
Vectoriality: force is a vector, which has both magnitude and direction
simultaneity: the force proced and disappeared at the same time
independence: the effect of one force does not affect the effect of another
includes three elements: the size, direction and action point of the force. The accurate expression of the three elements of force by a directed line segment is called the diagram of force. The size is represented by the length of a scaled line segment, the direction is represented by an arrow, the point of action is represented by an arrow or the tail of an arrow, and the straight line along which the direction of a force follows is called the line of action of a force. The diagram of the force is used for the calculation of the force. When the judgment power is large, we must pay attention to the scale of the line segment, because even if one line segment is longer than another line segment, but the scale of the long line segment is also longer, the force represented by the short line segment is not necessarily smaller than that represented by the long line segment
∵ f floating = g = mg = 1kg * 10N / kg = 10N
volume of object v = m / P = 1kg / 0.6 × 103
kg/m3≈0.002m³
buoyancy when the object intrudes into the water
F floating = P water GV row = 20n
no force analysis was carried out before the force was applied to the object
the object received 10N gravity and 10N buoyancy. If the force was applied to make it completely submerge, the buoyancy was 20n
and there was 10N gravity
so 10N buoyancy was applied
1) common force
1. Gravity g = Mg (vertically downward, g = 9.8m/s2 ≈ 10m / S2, acting point at the center of gravity, applicable to the earth's surface)
2. Hooke's law f = KX {direction along the recovery deformation direction, K: stiffness coefficient (n / M), X: deformation variable (m)}
3. Sliding friction f = μ FN {is opposite to the relative motion direction of the object, μ: Friction coefficient, FN: positive pressure (n)}
4. Static friction 0 ≤ fstatic ≤ FM (opposite to the direction of relative motion of the object, FM is the maximum static friction)
5. Gravitation f = gm1m2 / R2 (g = 6.67) × Electrostatic force F = kq1q2 / R2 (k = 9.0) × 7. Electric field force F = EQ (E: field strength n / C, Q: electric quantity C, the electric field force of positive charge is the same as the direction of field strength)
8. Ampere force F = bilsin θ θ When l ⊥ B: F = bil, B / / L: F = 0)
9. Lorentz force F = qvbsin θ θ When v ⊥ B: F = QVB, V / / B: F = 0)
note:
(1) the stiffness coefficient K is determined by the spring itself
(2) friction coefficient μ It has nothing to do with the pressure and contact area, but is determined by the material characteristics and surface condition of the contact surface
(3) FM is slightly larger than that of FM μ FN, generally regarded as FM ≈ μ FN;
(4) other related contents: static friction (size and direction) [see P8 in Volume 1]
(5) symbol and unit of physical quantity B: magnetic inction intensity (T), l: effective length (m), I: current intensity (a), V: velocity of charged particle (M / s), Q: charge of charged particle (charged body) (c)
(6) the direction of Ampere force and Lorentz force are determined by left-handed rule
2) the composition and decomposition of forces
1. The composition of forces on the same line is in the same direction: F = F1 + F2, reverse: F = F1-F2 (F1 & gt; F2)
2. Synthesis of mutual angular force:
F = (F12 + F22 + 2f1f2cos) α) 1 / 2 (cosine theorem) F1 ⊥ F2: F = (F12 + F22) 1 / 2
3. Range of resultant force: | F1-F2 | ≤ f ≤| F1 + F2 |
4. Orthogonal decomposition of force: FX = fcos β, Fy=Fsin ββ Is the angle TG between the resultant force and the x-axis β= FY / FX)
note:
(1) the composition and decomposition of forces (vectors) follow the parallelogram rule
(2) the relationship between resultant force and component force is equivalent substitution relationship, which can replace the joint action of component force with resultant force, and vice versa
(3) in addition to the formula method, the drawing method can also be used to solve the problem. In this case, the scale should be selected and the drawing should be strict
(4) when the value of F1 and F2 is fixed, the angle between F1 and F2 is smaller α The larger the angle, the smaller the resultant force
(5) the combination of forces on the same straight line can take the positive direction along the straight line, and the direction of the force can be represented by a sign, which is simplified to an algebraic operation.
density: ρ= M / V
gravity: g = mg
pressure: P = f / S ρ Liquid GV row
floating: F floating = g matter
lever balance condition: F1 × L1=F2 × L2
work: w = FS
Power: P = w / T = FV
mechanical efficiency: η= W useful / W total = GH / Fs = g / FN (n is the number of strands of pulley block)
1) common force
1. Gravity g = mg
(vertical downward, g = 9.8m / S2 ≈ 10m / S2, acting point at the center of gravity, applicable to the earth's surface)
2. Hooke's law f = KX
{direction along the recovery deformation direction, K: stiffness coefficient (n / M), X: deformation variable (m)}
3. Sliding friction f = μ FN
{opposite to the relative motion direction of the object, μ: Friction coefficient, FN: positive pressure (n)}
4. Static friction 0 ≤ F, static ≤ FM
(opposite to the relative motion direction of the object, FM is the maximum static friction)
5. Gravitation f = gm1m2 / r2
(g = 6.67) × Electrostatic force F = kq1q2 / r2
(k = 9.0) × 7. Electric field force F = EQ
(E: field strength n / C, Q: electric quantity C, the electric field force of positive charge is the same as the direction of field strength)
8. Ampere force F = bilsin θ< br /> θ When l ⊥ B: F = bil, B / / L: F = 0)
9. Lorentz force F = qvbsin θ< br /> θ When v ⊥ B: F = QVB, V / / B: F = 0)
note:
(1) the stiffness coefficient K is determined by the spring itself
(2) friction coefficient μ It has nothing to do with the pressure and contact area, but is determined by the material characteristics and surface condition of the contact surface
(3) FM is slightly larger than that of FM μ FN, generally regarded as FM ≈ μ fn;
(4) other related contents: static friction force (size and direction) [see volume 1 P8]
(5) symbol and unit of physical quantity B: magnetic inction intensity (T), l: effective length (m), I: current intensity (a), V: velocity of charged particle (M / s), Q: electric quantity of charged particle (charged body) (c)
(6) the direction of Ampere force and Lorentz force are determined by left-handed rule< 2) the composition and decomposition of forces
1. The composition of forces on the same line is in the same direction: F = F1 + F2,
reverse direction: F = F1-F2
(F1 & gt; The synthesis of angular force:
F = (F12 + F22 + 2f1f2cos α) 1 / 2 (cosine theorem)
F1 ⊥ F2: F = (F12 + F22) 1 / 2
3. Range of resultant force: | F1-F2 | ≤ f ≤| F1 + F2 |
4. Orthogonal decomposition of force: FX = fcos β, fy=fsin ββ Is the angle TG between the resultant force and the x-axis β= (FY / FX)
note:
(1) the composition and decomposition of forces (vectors) follow the parallelogram rule
(2) the relationship between resultant force and component force is equivalent substitution relationship, which can replace the joint action of component force with resultant force, and vice versa
(3) in addition to the formula method, the drawing method can also be used to solve the problem. In this case, the scale should be selected and the drawing should be strict
(4) when the value of F1 and F2 is fixed, the angle between F1 and F2 is smaller α The larger the angle, the smaller the resultant force
(5) the combination of forces on the same straight line can take the positive direction along the straight line, and the direction of the force can be represented by a sign, which is simplified to an algebraic operation.
W = FS when lifting an object, w = GH, w = Pt
formula of power
P = w / T, P = w / T = FS / T = Fv (v = P / F)
formula of active work
formula of lifting height, w = GH level, w = FS, w = wtotal-w amount
formula of total work
wtotal = fs (s = NH) wtotal = wtotal/ η Wtotal = wyou + wtotal = ptotal
Force is proced by the interaction between matter (object) and matter (object). The size, direction and action point of force are the three elements of force. Or the rate of change of momentum over time
formula:
F = ma (Newton's second law formula)
G = MGG is the acceleration of gravity, and the gravity of an object with a mass of 1kg is about 9.8N (affected by latitude)
F= μ FN μ For dynamic friction coefficient, FN is pressure
extended data:
application scope
it is very accurate in many occasions. Classical mechanics can be used to describe the motion of body size objects (such as gyroscopes and baseball), many celestial bodies (such as planets and galaxies), and some micro scale objects (such as organic molecules)
in low-speed objects, classical mechanics is very practical. Although Einstein put forward the theory of relativity, in our life, we hardly encounter high-speed motion (light speed level), so we will still use classical mechanics to explain various phenomena
However, in high-speed motion or between objects of great mass, the classical mechanics is "more than the heart but less than the force". This is the category of modern physics(1) the relationship among density, mass and volume: ρ ﹦m/V ,m= ρ V,V= m/ ρ< br /> ρ--- Density --- kg / m3 (kg / m3), m --- mass --- kg (kg), V --- volume --- m3 (M3)
(2) relationship among velocity, distance and time: v = s / T, s = VT, t = s / V
V --- velocity --- M / S (M / s), s --- distance --- m (m), t --- time --- s (s)
(3) relationship between gravity and mass: g = mg, M = g / g, g = g / M
G --- gravity --- n (Newton), m --- mass --- kg (kg), g = 9.8n/kg
(4) balance condition of lever: F1 × L1 = F2 × L2
F1 --- power --- n (n), L1 --- power arm --- m (m), F2 --- resistance --- n (n), L2 --- resistance arm --- m (m)
(5) calculation of pulley block: F = (1 / n) g, s = NH
f --- tensile force --- n (n), G --- gravity --- n (n), n --- number of rope segments,
s --- distance of rope movement --- m (m), and (6) definition of pressure: P = f / S (applicable to any kind of pressure calculation), f = PS, s = f / P
P --- pressure --- PA (PA), f --- pressure --- n (Newton), s --- stressed area --- M2 (square meter)
(7) calculation of liquid pressure: P= ρ gh, ρ= p/gh,h=p/ ρ G
P --- pressure --- PA (PA) ρ--- Liquid density --- kg / m3 (kg / m3), g = 9.8n/kg, H --- liquid depth --- m (m)
(8) calculation of buoyancy: F floating = g row= ρ Liquid GV row (immersion, V row = V matter),
F float = G-F pull (commonly used in experiments), f float = g matter (suspension, floating)
F float -- buoyancy -- N (Newton), g row -- liquid gravity -- N (Newton), G = 9.8n/kg,
V row -- liquid volume -- m3 (M3),
V row -- liquid gravity -- N (Newton),
V row (9) calculation of work: w = f · s (commonly used in horizontal direction)
= g · H (commonly used in vertical direction)
W --- work --- J (joule), f --- force --- n (Newton), s --- distance --- m (meter), G --- gravity --- n (Newton), H --- distance --- m (meter)
(10) calculation of mechanical efficiency: w = g · h, W total = f · s, η= Wyou / wtotal
wyou --- useful work --- J (joule), G --- gravity --- n (Newton), H --- distance --- m (meter)
wtotal --- total work --- J (joule), f --- force --- n (Newton), s --- distance --- m (meter)
(11) power calculation: P = w / T = FS / T = f · V, w = Pt, t = w / P
P --- power --- w (watt), w --- work --- J (joule), w --- energy --- J (joule), w --- power --- J (joule) T --- time --- s (seconds), V --- velocity --- M / S (meters per second)
(12) calculation of heat: q = cm △ T, C = q / m △ T, M = q / C △ T,
△ t = q / cm, △ t = t high temperature --- t low temperature
Q --- absorbed (released) heat --- J (coke), C --- specific heat capacity --- J / (kg · ℃) [coke / (kg ·℃)],
m --- mass --- kg (kg), and Δ T -- temperature difference -- ℃ (centigrade)
1 horsepower = 735 watts
so 180 million = 180000 / 735 = 244.898 horsepower
pro, please adopt, your adoption is my power, thank you.