Force, Mass andMomentum

Newton’s Second Law: F = ma

• 1 newton = 1 kg 1 m/s²∙

• Force: 1 pound = 4.45 newtons• Your weight is the force of gravity: F = mg• g = 10 N/kg• 225 pounds = 1000 newtons

Momentum = p = mv• Units: p = mv Units: kg m/s ∙• Newton’s First Law : An object in motion continues in motion• If there are no forces, • velocity doesn’t change Δv= 0• momentum doesn’t change Δp = 0

Δ = delta = difference = change• F = ma = mΔv/ t = m(vf – vo)/t

• = (mvf – mvo)/t = (pf – po)/t = Δp / t

• F = Δp / t The rate of change of momentum equals force.

Impulse• F = Δp / t

The rate of change of momentum equals force.• If we mulitply by t• F t = ∙ Δp Ft is called impulse• (F s = work = ∙ Δ Energy)• • Impulse = Change in Momentum• newton second = kg m / s∙ ∙• (1 newton = 1 kg 1 m/s²) ∙

The Third Law

• Newton’s Third Law:• “If A pushes B then B pushes A”• (in opposite directions)

• FA = −FB

• Time is equal t F∙ A = − t F∙ B

• The impulse is equal and opposite• ΔpA = − ΔpB

• ΔpA + ΔpB = 0

• Momentum is conserved

Conservation

• Energy is Conserved

• Momentum is Conserved

• Mass is Conserved