A collision can cause the objects involved to change motion and/or change shape.

Energy transfer occurs during a collision.

There is a force(s) between objects when they make contact during a collision.

All solid objects deform elastically when force is applied to them, up to a point.

Different objects have different elastic limits, which is the maximum amount of deformation an object can withstand, beyond which it will deform permanently.

Different objects have different breaking points, which is the maximum amount of deformation an object can withstand, beyond which it will crack or split apart.

The type of material, the shape, and the thickness of an object all affect (a) how much it deforms when a force is applied to it, (b) its elastic limit and, (c) its breaking point.

Objects that make contact with each other apply equally strong forces on each other in opposite directions.

Objects that collide apply an equally strong peak force (maximum force) on each other during the collision.

A free body diagram can help represent the forces on the objects in a collision by considering each object separately.

Increasing the speed or mass of a moving object increases its kinetic energy (KE).

The more KE that objects in a system have, the higher the peak forces they can produce in a collision.

In an investigation with multiple independent variables it is important to keep track of which variables are remaining constant and which are changing

The more KE an object has the more damage it can do in a collision

The more KE an object has the more you have to push against the direction of its motion to get it to stop

The KE of an object is directly proportional to its mass, the KE of an object is proportional to the square of its speed

The more force you apply to an object the more that object speeds up.

It takes more force to speed up a more-massive object the same amount as a lower-mass object.

Potential energy can be stored in some systems when you change the shape or arrangement of parts in that system (e.g., a spring).

Contact forces transfer energy between different objects or subsystems within the larger cart-launcher system.

Friction is a contact force due to interaction between surfaces in contact and is produced by the bumps (roughness) on surfaces as they push against each other.

Interactions due to friction and air resistance apply contact forces to a moving object that are in a direction that is opposite its motion.

Force interactions due to friction and air resistance transfer energy to the surfaces of the objects that slide over each other; this results in an increase in particle-level kinetic energy (a temperature increase).

Energy can be transferred to and from collisions between objects and particles in the air.