GCSE Physics (AQA)

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Explosions & Recoil

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Forces Momentum

Explosions & Recoil

3:20 Using the Conservation of Momentum
Spec 4.5.7.2
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  • An explosion provides a force that pushes objects away from the point of origin.
  • An example of an explosion is a bomb, which releases a large amount of energy from a chemical reaction.
  • The explosion creates an outward force that pushes everything away from the point of the explosion.
  • Shrapnel, or small pieces of material, are projected away from the bomb during the explosion.
  • Particles in an explosion are objects with mass, but their shape or volume is not considered.
  • The total momentum of the particles after an explosion is the same as the total momentum before the explosion.
  • Momentum is the product of mass and velocity and is conserved unless an external force acts on the system.
  • A bomb and its shrapnel can be treated as a closed system, with the explosion as the only force.
  • If the bomb was stationary before the explosion, the total momentum was zero.
  • After the explosion, the vector sum of all particle momentum adds to zero, conserving momentum.
  • Momentum acts as a vector; momentum in one direction is canceled by momentum in the opposite direction.
  • In exams, one-dimensional examples with two or three particles are common.
  • A gun recoils when fired to balance the momentum of the fired bullet.
  • The gun is initially stationary; firing causes the bullet to gain momentum, P.
  • The gun recoils with the same momentum, P, in the opposite direction.
  • Momentum vectors are equal and opposite, adding to zero, conserving system momentum after the explosion.

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