5.7.3 Collisions

• What are collisions in physics?

  Interactions between two or more objects where they come into contact and exert forces on each other
• Why is understanding collisions essential?

  It helps analyze how objects move and interact in various scenarios
• What are the two main types of collisions?

  • Elastic Collisions
  • Inelastic Collisions
• What is the definition of elastic collisions?


  Collisions in which both momentum and kinetic energy are conserved
• What are the characteristics of elastic collisions?

  Total momentum and total kinetic energy are conserved before and after the collision
• Can you give an example of an elastic collision?

  Collisions between gas particles or idealized collisions between hard spheres
• What is the definition of inelastic collisions?

  Collisions in which momentum is conserved, but kinetic energy is not
• What happens to kinetic energy in inelastic collisions?

  Some kinetic energy is converted into other forms of energy, such as heat or sound
• Can you provide an example of an inelastic collision?

  Car crashes or collisions between soft objects like clay
• What is the principle of conservation of momentum in collisions?

  • The total momentum of a system of colliding objects remains constant if no external forces act on it.
  • Total Momentum Before = Total Momentum After
• How is total momentum calculated before a collision between two objects?


  By summing the products of mass and initial velocity for both objects
• What is the mathematical formulation for total momentum before and after a collision?

  Before: \( m_1 v_{1i} + m_2 v_{2i} \); After: \( m_1 v_{1f} + m_2 v_{2f} \)
• What is the mass and initial velocity of Trolley A in the elastic collision example?

  Mass = 2 kg, Initial velocity = 4 m/s
• What is the total momentum before the collision in the elastic collision example?

  8 kg·m/s
• What is the final velocity of Trolley B after the elastic collision?

  2 m/s
• How is kinetic energy calculated before the collision in the elastic collision example?

  By using the formula \( \frac{1}{2} m v^2 \) for both trolleys
• What is the total kinetic energy before the collision in the elastic collision example?


  16 J
• What is the mass of the ball in the inelastic collision example?

  1 kg
• What happens to the two balls after the inelastic collision?

  They stick together and move as a single unit
• What is the common velocity of the two balls after the inelastic collision?

  Approximately 1.67 m/s
• What are some real-world applications of collision physics?

  • Automotive Safety: Designing crumple zones in cars
  • Sports: Analyzing collisions in games like football or billiards
  • Particle Physics: Studying subatomic particle collisions in accelerators
• What is the summary of elastic and inelastic collisions?

  • Elastic Collisions: Both momentum and kinetic energy are conserved.
  • Inelastic Collisions: Momentum is conserved, but kinetic energy is not; it is transformed into other forms of energy.
• Why is understanding collisions important?

  • Helps predict outcomes of interactions between objects
  • Fundamental to everyday applications and advanced scientific research