Physics Chap 7
Kinetic Energy conservation equation
1/2m₁v² =1/2m₁Vf₁² + 1/2m₂Vf₂²
Impulse equation
F ∆t
Other equation for change in momentum
F∆t = m∆v
Big Idea
Momentum is conserved in all collisions, as long as external forces do not act
Momentum conservation equation
P total = m₁v₁ +m₂v₂
Total momentum
Ptotal = p₁ + p₂ + ...
Two dimension collision equations
Px₁ = Px₂ Py₁ = Py₂
Elastic collision in one dimension, when m₁ is moving with an initial velocity of v and m₂ is initially at rest. The velocities of the masses after the collision is seen with this equation (Vf₁)
Vf₁ = ((m₁-m₂) / (m₁+m₂)) *v
Elastic collision in one dimension, when m₁ is moving with an initial velocity of v and m₂ is initially at rest. The velocities of the masses after the collision is seen with this equation (Vf₂)
Vf₂ = ((2m₁)/(m₁+m₂)) *v
Momentum conservation applies to ______ collisions.
all
if the velocity changes direction, the momentum does what?
also changes direction
Only ______ forces can change a system's momentum
external
Internal force
forces acting between objects within the system
External forces
forces exerted on a system by something outside of the system
Conservation of momentum
if the total force acting on an object is zero, its momentum cannot change. p₁ = p₁
Recoil
is a result of momentum conservation
A railroad car of mass m moving with speed v collides and stick to an identical railroad car that is initially at rest. After the collision what is the final kinetic energy compared to the initial?
it is one-half the initial kinetic energy
Si unit for impulse
kg * m/s
Units of momentum
kg * m/s
Elastic Collision
kinetic energy is conserved (KE₂ = KE₁)
Inelastic collision
kinetic energy is not conserved, (total energy is conserved, but just transformed to other forms)
Magnitude of momentumequation
mv (mass *speed)
Momentum equation
mv (mass* velocity)
Impulse shows what?
the change in the object's momentum
What determines the direction of an impulse?
the force
Total momentum of a system is the _______ (2) of the momentums of all the individual objects.
vector sum
Completely inelastic collision
when the objects stick together
Momentum can be resolved into its ______.
x and y components
Impulse equation (in terms of momentum)
∆p (p₂ - p₁)
Change in momentum equation
∆p = p₂ - p₁
F total = ?
∑F external
