Physics / Momentum & Collisions

In a closed system, momentum and total energy are (both conserved/not conserved).

both conserved

Describe a perfect inelastic collision.

When two objects collide, stick together, and move as one mass, with the same velocity.

Describe a general inelastic collision.

When two objects collide and bounce off each other. Their final velocities may be different.

In an elastic collision, the initial kinetic energy of the system is (less than/equal to/greater than) the final kinetic energy.

equal to

In an elastic collision, the kinetic energy of each of the objects (can change/never changes). The system’s kinetic energy (does change/does not change).

can change, does not change

Types of collisions:

• General inelastic collision

• Perfect inelastic collision

• Elastic collision

• Explosion

In which of these is momentum conserved?

All of them.

Types of collisions:

• General inelastic collision

• Perfect inelastic collision

• Elastic collision

• Explosion

In which of these is kinetic energy conserved?

Only in elastic collisions. Kinetic energy is converted to other forms of energy in inelastic collisions, and the release of potential energy increases kinetic energy in explosions.

Equation for general inelastic and elastic collisions.

m₁v₁ + m₂v₂ = m₁v₁’ + m₂v₂’

Equation for perfect inelastic collisions.

m₁v₁ + m₂v₂ = (m₁ + m₂)v'

Equation for explosions

(m₁ + m₂)v = m₁v₁’ + m₂v₂’

The equation for conservation of momentum is p₁ + p₂ = p₁’ + p₂’. It can also be written as:

m₁v₁ + m₂v₂ = m₁v₁' + m₂v₂'

The conservation of kinetic energy can be written as KE₁ + KE₂ = KE₁’ + KE₂’

It can also be written as:

½m_av_a + ½m_bv_b = ½m_av_a’ + ½m_bv_b’

When two objects with the same mass collide, their ending velocity is…

equal and opposite to their initial velocity.

When a large mass object strikes a smaller mass object at rest, the large mass’ velocity (stays the same/doubles/halves). The small mass’ velocity ____.

stays the same, is double the larger mass’ velocity.

When a smaller mass object strikes a larger mass object at rest…

The smaller mass’ velocity becomes ____.

The larger mass’ velocity _____.

equal and opposite to its initial velocity, stays at 0