Collisions

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Collisions

A collision is any crash or interaction between two or more objects.

What is a collision?

Multiple Choice

Which of the following is NOT a collision?

• Two cars hit each other when at an intersection and each ends up in a different location.

• While playing pool, the white ball hits a solid, red ball and they ricochet off each other.

• A train locomotive latches onto a cargo second railway wagon.

• A wrecking ball crashes into the side wall of a large, abandoned building.

No!
There are two main types of collisions:
Elastic & Inelastic

Are all collisions the same?

These are crashes where the two objects get stuck together.

Since they're stuck together, they move as one, massive object; sharing one change in momentum.

​​Inelastic

These are crashes where the two objects hit each other then separate.

Since they separate, each object experiences their own changes in momentum after the crash.

Elastic

Match

Match the following

• Inelastic Crash

• Elastic Crash

• Not A crash

A slime hand tossed & sticks to a window

Bumper cars

Two lumps of playdoh squeezed into one

• A slime hand tossed & sticks to a window

• Bumper cars

• Two lumps of playdoh squeezed into one

Both cars share a new momentum with their total mass:
p = (m₁ + m₂) * v

Their masses combine.

After Crash

Each object has its own starting momentum. p₁ & p₂

The total momentum before the crash: p₁ + p₂

Before Crash

Inelastic Collisions

Each car has its own final momentum: p_1f & p_2f

The total momentum after the crash: p_1f + p_2f

After Crash

Each object has its own initial momentum. p_1i & p_2i

The total momentum before the crash: p_1i + p_2i

Before Crash

Elastic Collisions

Drag and Drop

In an ​

Placeholder

collision, objects crash and ​

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.

Drag these tiles and drop them in the correct blank above

inelastic

stick together

elastic

separate

Drag and Drop

In an ​

Placeholder

collision, objects crash and ​​

Placeholder

.

Drag these tiles and drop them in the correct blank above

inelastic

elastic

separate

stick together

The Law of Conservation of Momentum

"For a closed system,
The total momentum before an event
is equal to the total momentum
after an event"

Multiple Choice

Which of the following occurs for an inelastic collision?

• p_1i + p_2i -> p_1f + p_2f

• p_1i + p_2i -> p_f

  where...

  p_f = (m₁ + m₂) * v

Multiple Choice

Which is true of the law of conservation of momentum?

• Momentum is always conserved, no matter what.

• Momentum is always conserved in closed systems.

Multiple Choice

What does "(m₁+m₂)" mean?

• It means that, during an inelastic collision, the objects get stuck, so we combine their masses to find their combined final momentum.

• It means that you add two masses no matter the type of crash, in order to follow the law of conservation of momentum.

thank you!