Physics revising

[elen_nare]

I have my second physics exam tomorrow. If I get more then 7, I don't have to take the final exam, so I really want to do well. I think I'll be ok - I can do all the practice problems, and we got together to revise with some friends, so I'm fairly sure I know everything. I'm still a bit nervous though.

We're allowed to have printed notes and books in the exam, so I've just spent half an hour typing up all the formulae. Very tiring, especially with all the symbols, but I think they've come out rather well.

Masa inercial: resistencia de un sistema a modificar su estado de movimiento. Es aditiva y se conserva.

El momento Px se conserva siempre que el sistema esté en equilibrio (Σ F_externas = 0)

Choque Explosivo:

mb = - Va = |Va|

ma      Vb    |Vb|

Vb > Va => ma > mb

mbVb = - maVa

maVa + mbVb = 0

maVa = Pa = momento

Pa = - Pb

Choque Elástico:

maVa + mbVb = maV’a + mbV’b

Va - Vb = - V’a + V’b

Pa + Pb = P’a + P’b

V’a = 2mbVb + (ma - mb)Va V’b = 2maVa + (mb - ma)Vb

           ma + mb                                    ma + mb

ma = mb => V’a = Vb y V’b = Va

Choque Plástico:

maVa + mbVb = maV’a + mbV’b = (ma + mb)V’a

V’a = V’b

V a_/b = maVa + mbVb

                ma + mb

Centro de Masa:

X_CM = Σ miXi V_CM = Σ miVi

           Σmi                 Σmi

Fuerza:

F_media = ΔP      Variación del momento de c/cuerpo. Mide la intensidad de la colisión.

             Δt

dP = F => F = dmV = m.dV = ma

dt                      dt            dt

MRUV: a = (ΔV)²

                   2Δx

ΔPa + ΔPb = 0 => ΔPa = -ΔPb => Fa = - Fb

Superposición de fuerzas: F_total = Fa + Fb

Resortes:

F = -kΔx

En paralelo:

F₁ = k₁Δx } F = F₁ + F₂ = (k₁ + k₂) Δx   =>   k_e = k₁ + k₂

F₂ = k₂Δx }

En serie:

Δx₁ + Δx₂ = Δx }  =>  k_e = k₁ + k₂

k₂ Δx₂ = k_e Δx }                   k₁k₂

Polea:

T₁ - m₁g = m₁a₁ }   =>  T = 2m₁m₂ g

T₂ - m₂g = m₂a₂ }                m₁ + m₂

a₁ = - a₂ }   =>   a₁ = m₂ - m₁

T₁ = T₂ }                    m₂ + m₁