Energy & Classification Of Collisions Flashcards
Relative Velocity
Vector difference between velocity of two bodies
With colliding carts, in most cases, there is no change in relative velocity because velocity magnitude is the same before and after collision.
Relative Speed
Magnitude of relative velocity
Elastic Collision
Collision in which relative speed before collision is the same as relative speed after collision.
E.g Ball Bouncing off Hard Floor
Kinetic Energy & Momentum during Elastic Collision
Both the momentum and kinetic energy are conserved.
Inelastic Collision
A collision in which relative speed is not conserved.
E.g Tennis Ball to Floor
Kinetic Energy & Momentum during Inelastic Collision
Momentum is conserved but kinetic energy is not.
Totally Inelastic Collision
Collision in which two objects move together after collision so their relative speed is zero.
E.g Dropping dough ball to the floor
Kinetic Energy & Momentum during Totally Inelastic Collision
The momentum is conserved, kinetic energy is lost and converted to other forms of energy (internal)
Kinetic Energy
Observable energy of motion of an object
Kinetic Energy Equation
K = 1/2mv^2
K = 1/2(m1 + m2)v^2
State
Every physical variable of an object: Shape, temperature, etc.
Process
Transformation of a system from initial state to final state.
E.g Collision changing motion of state of objects; ice melting
Irreversible Changes
Changes that occur in state of colliding objects that cannot undo themselves
This occurs in ALL Inelastic Collision.
Reversible Change
No permanent changes in state of colliding objects
This occurs in elastic collisions.
Internal Energy
Quantity of energy having same units as Kinetic Energy within state of object.
An increase in internal energy decreases kinetic energy as one form of energy is converted to another form of energy. The sum of the energy system does not change.
True or False: Energy of a system does not change during collision.
True
State Changes and Associated Internal Energy
Temperature - Thermal
Chemical - Chemical
Reversible Change in Shape - Elastic Energy
Phase Change - Transformation Change
Closed System
Any system in which energy is constant.
No matter can enter or exit system. It energy can be exchanged with surroundings.
Conservation of Energy
Total energy in closed system remains constant overtime.
What happens to relative velocity after Elastic Collision?
Relative Velocity always changed signs.
v2i - v1i = -(m2f - v2f)
Momentum Equation of Elastic Collision
m1v1i + m2v2i = mfv1f + mfv2f
Coefficient of Restitution
Ratio of relative speed; tells us how much initial relative speed is restored after collision.
e = v12f / v12i
Conservation of Energy Equation
E = K + Eint
In Closed System: Ei = Ef
