Momentum and impulse

• What is the formula for momentum?

  p = mv
• What type of quantity is momentum?

  Momentum is a vector quantity
• If a car has a mass of 1200 kg and travels at 20 m/s, what is its momentum?

  24,000 kgms^-1
• In which direction does momentum act?

  In the same direction as velocity
• How is positive and negative momentum defined in this context?

  Right is +ve, left is -ve
• How do you calculate total momentum of a system?

  Add all individual momentums together
• What is the total momentum of a system with a mass of 1800 kg at 30 m/s and a mass of 1600 kg at -35 m/s?

  -2000 kgms^-1
• What does conservation of linear momentum state?

  Total momentum before equals total momentum after
• What is the equation for conservation of momentum using initial speed?

  m1u1 + m2u2 = m1v1 + m2v2
• What are the three types of momentum calculations?

  • Collide-and-lock collisions
  • Collide-and-split collisions
  • Explosions
• In a collide-and-lock collision, what is the final velocity if m1 = 8 kg, u1 = 4 m/s, and m2 = 6 kg, u2 = 0 m/s?

  2.3 m/s to the right
• In a collide-and-split collision, what is the final velocity if m1 = 8 kg, u1 = 4 m/s, and m2 = 6 kg, u2 = -2 m/s?

  -0.5 m/s or 0.5 m/s to the left
• In an explosion, what is the total momentum before the event?

  0 kgms^-1
• What is the difference between elastic and inelastic collisions?

  Elastic conserves both energy and momentum
• In an inelastic collision, if Ek1 + Ek2 = 76 and is not equal to 49, what can be concluded?

  The collision is inelastic
• How is change in momentum calculated?

  Δp = mv - mu
• What is the change in momentum of an 8 kg trolley moving from 4 m/s to -0.5 m/s?

  -36 kgms^-1
• What does impulse equal in terms of momentum?

  Impulse equals change in momentum
• What are the units of impulse?

  Ns (Newton Seconds)
• What does the area under a force-time graph represent?

  The impulse applied to the object
• If a cue ball of mass 0.2 kg is accelerated to 2 m/s by a force lasting 50 ms, what is the force exerted?

  8 N
• What is the impulse of a tennis ball hit by a racket if the area under the force-time graph is 4 Ns?

  4 Ns
• What is the speed of a tennis ball of mass 0.1 kg after being hit if the impulse is 4 Ns?

  40 m/s
• What is the force exerted on a 0.1 kg tennis ball rebounding at -15 m/s after being struck?

  -50 N
• How do crumple zones and airbags enhance car safety?

  • Increase time of collision
  • Decrease average force
  • Reduce risk of injury
• If Car A (1500 kg) stops in 1.5 s and Car B (1500 kg) stops in 3.5 s, how do their average forces compare?

  Car B has a lower average force
• What does Newton's 3rd Law state about forces?

  Every action has an equal and opposite reaction
• How can conservation of momentum be used to prove Newton's 3rd Law?

  By showing forces are equal and opposite
• What were the results of the trolley experiment regarding forces?

  FA = -FB confirms equal forces