Chapter 4 Flashcards
Momentum & Torque (19 cards)
Momentum (p)
p = mv
Elastic collision equation between (roughly) equal masses
m₁v₁i + m₂v₂i = m₁v₁f + m₂v₂f
Inelastic collision equation between (roughly) equal masses
m₁v₁i = (m₁+m₂)vf
Torque (τ)
τ=r(Fsinθ)
Work (w) vs. Torque (τ)
Work uses parallel force x distance
Torque uses perpendicular force x distance
Impulse (J) equation
J= Δmv
J= F(avg)*Δt(time of collision)
J=mv₂-mv₁
Collisions where momentum of 2 objects is conserved (no ΔKE)
Both objects experience the same magnitude of impulse
Collisions where KE of objects Δes
Inelastic collisions (KE is lost to friction, an internal force of inelastic collisions)
Inelastic collision definition
Collisions where objects deform, often stick together, and usually slow down after collision. Energy is not conserved (ΔKE)
Momentum calculation short cut
The ratio of the objects masses must equal the reatio of their Δs in v.
Relationship of kinetic energy to collision
If KE is lost, an inelastic collision occurred.
Generally, a decrease in v = lost KE. Momentum is conserved because momentum is only lost via external forces (friction is internal to collision so doesn’t count)
Torque definition
The measurement of the ability of a force to cause rotation about a given pivot point (N-m). Created when force is applied perpendicularly
Fulcrum
The point about which an object rotates
Rotational equilibrium definition
A system experiencing no rotational acceleration (τ=0)
Impulse definition
impact force on a colliding object that changes the objects momentum
Two conditions for rigid body equilibrium
Fnet=0
τnet=0
Rotational motion definition
Rotation of an object about an axis
Mechanical advantage of a lever
distance of fulcrum / distance of weight
d(fulcrum) / d(weight)
Long (effort) arm / short (load) arm
Calculating applied force over a lever
F(applied) = mg*d(weight)/d(fulcrum)
