Form of mechanics

Kinematic

In Coordinated Cartesian

\overrightarrow{OM}=x\overrightarrow{u_x}+y\overrightarrow{u_y}+z\overrightarrow{u_z}

\ overrightarrow {v} (M) = \ frac {\ text {D} \ overrightarrow {OM}} {\ text {D} T} = \ frac {\ text {D} X} {\ text {D} T} \ overrightarrow {u_x} + \ frac {\ text {D} there} {\ text {D} T} \ overrightarrow {u_y} + \ frac {\ text {D} Z} {\ text {D} T} \ overrightarrow {u_z}

\ overrightarrow {has} (M) = \ frac {\ text {D} \ overrightarrow {v} (M)}{\ text {D} T} = \ frac {\ text {D} ^2 \ overrightarrow {OM}} {\ text {D} t^2} = \ frac {\ text {D} ^2 X} {\ text {D} t^2} \ overrightarrow {u_x} + \ frac {\ text {D} ^2 there} {\ text {D} t^2} \ overrightarrow {u_y} + \ frac {\ text {D} ^2 Z} {\ text {D} t^2} \ overrightarrow {u_z}

In Coordinated cylindrical

\ overrightarrow {OM} = \ rho \ overrightarrow {u_ \ rho} +z \ overrightarrow {u_z}

\ overrightarrow {v} (M) = \ frac {\ text {D} \ overrightarrow {OM}} {\ text {D} T} = \ frac {\ text {D} \ rho} {\ text {D} T} \ overrightarrow {u_ \ rho} + \ rho \ frac {\ text {D} \ phi} {\ text {D} T} \ overrightarrow {u_ {\ phi}} + \ frac {\ text {D} Z} {\ text {D} T} \ overrightarrow {u_z}

\ overrightarrow {has} (M) = \ frac {\ text {D} \ overrightarrow {v} (M)}{\ text {D} T} = \ frac {\ text {D} ^2 \ overrightarrow {OM}} {\ text {D} t^2} = \ left (\ frac {\ text {D} ^2 \ rho} {\ text {D} t^2} - \ rho \ left (\ frac {\ text {D} \ phi} {\ text {D} T} \ right) ^2 \ right) \ overrightarrow {u_ \ rho} + \ left (2 \ frac {\ text {D} \ rho} {\ text {D} T} \frac {\ text {D} \ phi} {\ text {D} T} + \ rho \ frac {\ text {D} ^2 \ phi} {\ text {D} t^2} \ right) \ overrightarrow {u_ {\ phi}} + \ frac {\ text {D} ^2 Z} {\ text {D} t^2} \ overrightarrow {u_z}

While using: \ displaystyle \ frac {\ text {D} \ overrightarrow {u_ \ rho}} {\ text {D} T} = \ frac {\ text {D} \ phi} {\ text {D} T} \ overrightarrow {u_ {\ phi}} and \ frac {\ text {D} \ overrightarrow {u_ {\ phi}}} {\ text {D} T} = \ frac {\ text {D} \ phi} {\ text {D} T} \ overrightarrow {u_ \ rho}

In Coordinated spherical

\overrightarrow{OM}=r\overrightarrow{u_r}

\ overrightarrow {v} (M) = \ frac {\ text {D} \ overrightarrow {OM}} {\ text {D} T} = \ frac {\ text {D} R} {\ text {D} T} \ overrightarrow {u_r} +r \ frac {\ text {D} \ theta} {\ text {D} T} \ overrightarrow {u_ {\ theta}} +r \ frac {\ text {D} \ varphi} {\ text {D} T} \ sin \ theta \ overrightarrow {u_ \ varphi}

\ overrightarrow {has} (M) = \ frac {\ text {D} \ overrightarrow {v} (M)}{\ text {D} T} = \ frac {\ text {D} ^2 \ overrightarrow {OM}} {\ text {D} t^2} =a_r \ overrightarrow {u_r} +a_ \ theta \ overrightarrow {u_ \ theta} +a_ \ varphi \ overrightarrow {u_ \ varphi}

with:

a_r= \ left (\ frac {\ text {D} ^ 2r} {\ text {D} t^2} - R \ left (\ frac {\ text {D} \ theta} {\ text {D} T} \ right) ^2+r \ left (\ frac {\ text {D} \ varphi} {\ text {D} T} \ right) ^2 \ sin^2 \ theta \ right)

a_ \ theta= \ left (R \ frac {\ text {D} ^2 \ theta} {\ text {D} t^2} +2 \ frac {\ text {D} R} {\ text {D} T} \ frac {\ text {D} \ theta} {\ text {D} T} - R \ left (\ frac {\ text {D} \ varphi} {\ text {D} T} \ right) ^2 \ sin \ theta \ cos \ theta \ right)

a_ \ varphi= \ left (R \ frac {\ text {D} ^2 \ varphi} {\ text {D} t^2} \ sin \ theta +2 \ frac {\ text {D} R} {\ text {D} T} \ frac {\ text {D} \ varphi} {\ text {D} T} \ sin \ theta + 2r \ frac {\ text {D} \ varphi} {\ text {D} T} \ frac {\ text {D} \ theta} {\ text {D} T} \ cos \ theta \ right)

Change of reference frame

Speed of drive: \ overrightarrow {v_e} (M) = \ displaystyle \ left (\ frac {\ text {D} \ overrightarrow {OO'}} {\ text {D} T} \ right) _R+ \ overrightarrow {\ Omega} \ wedge \ overrightarrow {O' M}

Law of composition speeds: \ overrightarrow {v_R} (M) = \ overrightarrow {v_ {R'}} (M) + \ overrightarrow {v_e} (M)

Acceleration of drive: \ overrightarrow {a_e} (M) = \ displaystyle \ left (\ frac {\ text {D} ^2 \ overrightarrow {OO'}} {\ text {D} t^2} \ right) _R+ \ frac {\ text {D} \ overrightarrow {\ Omega}} {\ text {D} T} \ wedge \ overrightarrow {O' M} + \ overrightarrow {\ Omega} \ wedge \ left ( \ overrightarrow {\ Omega} \ wedge \ overrightarrow {O' M} \ right)

Acceleration of Coriolis: \ overrightarrow {a_c} (M) =2 \ overrightarrow {\ Omega} \ wedge \ overrightarrow {v_ {R'}} (M)

Law of composition of accelerations: \ overrightarrow {a_R} (M) = \ overrightarrow {a_ {R'}} (M) + \ overrightarrow {a_e} (M) + \ overrightarrow {a_c} (M)

Dynamics

Some forces

Weight: \ overrightarrow {P} =m \ overrightarrow {G}

Electromagnetic interaction: \ overrightarrow {F_ {1 \ rightarrow 2}} = \ displaystyle \ frac {1} {4 \ pi \ varepsilon_0} \ frac {q_1q_2} {(M_1 M_2) ^3} \ overrightarrow {M_1 M_2}

Gravitational interaction: \ overrightarrow {G_ {1 \ rightarrow 2}} = \ mathcal {G} \ displaystyle \ frac {m_1m_2} {(M_1 M_2) ^3} \ overrightarrow {M_1 M_2}

Tension of a spring: \ overrightarrow {T} =-k (l-l_0) \ overrightarrow {U} Fluid friction: \ overrightarrow {F} = \ lambda \ overrightarrow {v}

Inertia of drive: \overrightarrow{f_{i_e}}=-m\overrightarrow{a_e}

Inertia of Coriolis: \overrightarrow{f_{i_c}}=-m\overrightarrow{a_c}

Principle fundamental of dynamics

Vector momentum: \ overrightarrow {p} =m \ overrightarrow {v} (M)

Principle fundamental of dynamics: \ displaystyle \ frac {\ text {D} \ overrightarrow {p} (M)}{\ text {D} T} = \ sum \ overrightarrow {F} + \ overrightarrow {f_ {i_e}} + \ overrightarrow {f_ {i_c}}

Principle of the reciprocal actions: \ overrightarrow {f_ {has \ rightarrow B}} = \ overrightarrow {f_ {B \ rightarrow has}}

Energy aspect

Elementary work of a force: \ delta W (M) = \ overrightarrow {F} \ cdot \ text {D} \ overrightarrow {OM}

Work along a way \ Gamma_ {AB} : \ displaystyle W_ {has \ rightarrow B} = \ int_ {M \ in \ Gamma_ {AB}} \ delta W (M) = \ int_ {M \ in \ Gamma_ {AB}} \ overrightarrow {F} \ cdot \ text {D} \ overrightarrow {OM}

Power: \ mathcal {P} = \ displaystyle \ frac {\ delta W} {\ text {D} T}

kinetic Energy: E_c (M) = \ displaystyle \ frac {1} {2} mv^2 (M)

Theorem of the kinetic energy: \ displaystyle \ Delta E_c= \ sum W (F) +W (f_ {i_e}) +W (f_ {i_c})

Mechanical energy: E_m=E_c+E_p

Potential energy for some conservative forces

E_p (\ overrightarrow {P}) =mgz+C

E_p (\ overrightarrow {T}) = \ displaystyle \ frac {1} {2} K (l-l_0) ^2+C

E_p (\ overrightarrow {F}) = \ displaystyle \ frac {1} {4 \ pi \ varepsilon_0} \ frac {q_1q_2} {R}

E_p (\ overrightarrow {G}) = \ displaystyle - \ mathcal {G} \ frac {m_1m_2} {R}

Concept of Moment

kinetic Moment of a point M: \ overrightarrow {L_O} (M) = \ overrightarrow {OM} \ wedge m \ overrightarrow {v} (M)

\ overrightarrow {L_ {O'}} (M) = \ overrightarrow {L_O} (M) + \ overrightarrow {O' O} \ wedge m \ overrightarrow {v} (M)

Moment of a force \ overrightarrow {F} compared to O: \ overrightarrow {\ mathcal {M} _O} (\ overrightarrow {F}) = \ overrightarrow {OM} \ wedge \ overrightarrow {F}

\ overrightarrow {\ mathcal {M} _ {O'}} (\ overrightarrow {F}) = \ overrightarrow {\ mathcal {M} _O} (\ overrightarrow {F}) + \ overrightarrow {O' O} \ wedge \ overrightarrow {F}

Theorem of the kinetic moment: \ frac {\ text {D} \ overrightarrow {L_O} (M)}{\ text {D} T} = \ sum \ overrightarrow {\ mathcal {M} _O} (\ overrightarrow {F}) + \ overrightarrow {\ mathcal {M} _O} (\ overrightarrow {f_ {i_e}}) + \ overrightarrow {\ mathcal {M} _O} (\ overrightarrow {f_ {i_c}})

Oscillator

Harmonic oscillator (without damping):

Differential equation of the form: \ frac {\ text {D} ^2 X} {\ text {D} t^2} + \ omega_0^2x=0

own Pulsation: \ omega_0=; clean Period: T_0= \ displaystyle \ frac {2 \ pi} {\ omega_0}

Solution in the form: x (T) =A \ cos (\ omega_0 T) +B \ sin (\ omega_0 T)

The constant ones has and B are determined by the initial conditions.

Oscillator with factor of Damping \ lambda:

Differential equation of the form: \ frac {\ text {D} ^2 X} {\ text {D} t^2} +2 \ lambda \ frac {\ text {D} X} {\ text {D} T} + \ omega_0^2x=0

Three cases according to the value of the Discriminant of the characteristic equation:

\ Delta=4 (\ lambda^2- \ omega_0^2)

\ ast if \ Delta<0 is \ lambda< \ omega_0, then x (T) =e^ {- \ lambda T} \ left \ cos (\ Omega T) +B \ sin (\ Omega T) \ right (pseudoperiodic mode)

Pseudo-pulsation: \Omega=\sqrt{\omega_0^2-\lambda^2} ; Pseudo-period: T= \ displaystyle \ frac {2 \ pi} {\ Omega}

\ ast if \ Delta=0 is \ lambda= \ omega_0, then x (T) = (At+B) e^ {- \ lambda T} (mode criticizes)

\ ast if \ Delta>0 is \ lambda> \ omega_0, then x (T) =e^ {- \ lambda T} (Ae^ {\ sqrt {\ lambda^2- \ omega_0^2} .t} +Be^ {- \ sqrt {\ lambda^2- \ omega_0^2} .t}) (aperiodic mode)

In each case, the constant ones has and B are determined by the initial conditions.

Internal bonds

  • Mechanical
  • Mechanical Newtonian

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