Podcast
Questions and Answers
According to Newton's formulation, what is linear momentum defined as?
According to Newton's formulation, what is linear momentum defined as?
- Velocity divided by mass
- Force times time
- Mass times acceleration
- Mass times velocity (correct)
In an inelastic collision, both momentum and kinetic energy are conserved.
In an inelastic collision, both momentum and kinetic energy are conserved.
False (B)
What condition must be true for the expression $F\Delta t = \Delta p$ to represent impulse?
What condition must be true for the expression $F\Delta t = \Delta p$ to represent impulse?
Newton's 3rd Law of Motion
In an elastic collision, the relative speed of two objects ______ the collision is equal to the negative of their relative speed _______ the collision.
In an elastic collision, the relative speed of two objects ______ the collision is equal to the negative of their relative speed _______ the collision.
Match the collision type with the correct description:
Match the collision type with the correct description:
A blue ball collides with a red ball. During the collision, which of the following statements is true according to Newton's third law?
A blue ball collides with a red ball. During the collision, which of the following statements is true according to Newton's third law?
In what type of collision is kinetic energy converted into other forms of energy, such as heat or sound?
In what type of collision is kinetic energy converted into other forms of energy, such as heat or sound?
When solving collision problems, it is not important to define a boundary.
When solving collision problems, it is not important to define a boundary.
In a closed system with no external forces acting on it, what quantity is always conserved during a collision?
In a closed system with no external forces acting on it, what quantity is always conserved during a collision?
In a perfectly elastic collision with a stationary wall, a ball bounces off with the ______ speed it came in with.
In a perfectly elastic collision with a stationary wall, a ball bounces off with the ______ speed it came in with.
Flashcards
Linear Momentum
Linear Momentum
A vector quantity defined as mass times velocity (p=mv). It describes the quantity of motion an object has.
Inelastic Collision
Inelastic Collision
A collision where objects stick together. Momentum is conserved (if no external forces act), but kinetic energy is not.
Elastic Collision
Elastic Collision
A collision where objects bounce back. Both momentum and kinetic energy are conserved.
System Boundary
System Boundary
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Newton's Second Law and Momentum
Newton's Second Law and Momentum
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Conservation of Momentum
Conservation of Momentum
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Relative Velocities in Elastic Collisions
Relative Velocities in Elastic Collisions
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Study Notes
- Momentum is a vector derived from mass times velocity.
- Symbol for momentum is p.
- Calculated as p = mv where m is mass and v is velocity.
- Newton's second law states that the net sum of external forces equals the rate of change of momentum.
- Expressed as F = dp/dt.
- Impulse equals the change in momentum, where FΔt=Δp.
Collisions
- During collisions, the blue ball exerts a force on the red ball (FR), and the red ball exerts a force on the blue ball (FB)
- Newton's third law explains that FR = -FB which is a third-law force pair.
- States that FRΔt = -FBΔt, thus ΔpR = -ΔpB
- Total change in momentum, Δptotal = 0, provided there are no net external forces.
- Momentum is conserved if there are no net external forces.
- Kinetic energy is not conserved during inelastic collisions; some energy is converted to heat or sound.
- During elastic collisions momentum and kinetic energy are conserved if no net external forces are present
Inelastic Collisions
- Inelastic collisions occur when objects stick together after impact.
- Systems include both objects to exclude external forces.
- Linear momentum is conserved, but kinetic energy is not.
Special Case – Elastic Collisions
- Head on, one dimensional collision
- In cases were total momentum before collision is zero, m1v1 + m2v2 = 0
- Energy is conserved, since energy before and after is 1/2 m1v12 + 1/2 m2v22
- Momentum is conserved: ∑pi = 0 = ∑pf
- Relative velocity before equals the inverse of relative velocity after.
Solving Collision Problems
- Define the system's boundaries to determine external and internal forces.
- Simplify by including complicated forces as internal.
- Only one object in the system means all forces are external.
- Coordinate origin must be decided, positive directions should be determined, and vector components should be broken down in >1D
- It must be decided if the collision is elastic or inelastic.
- It must be decided if the objects stick together afterward.
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