Contact Forces

Contact Forces

Introduction

A collision occurs when two or more objects
come into contact, resulting in a transfer of
energy and changes in motion and shape. In this
presentation, we will explore the definition of a
collision, vocabulary related to collisions,
changes in motion and shape during collisions,
force and shape changes, the impact of mass
and speed, the role of friction and air resistance,
and real-world examples of collisions.

Definition of a Collision

A collision is an event where two or more
objects come into contact with each other,
resulting in a transfer of energy and often
changes in motion and shape.

Multiple Choice

Which best describes a collision?

• an event where two or more
  objects come into contact with each other

• an object moving

• an event that occurs multiple times when moving

• an event that occurs when any force acts on an object

Draw

Draw a collision.

Vocabulary Related to Collisions

●Momentum: Momentum is the product of an object's mass and velocity. It describes
the "mass in motion" and plays a crucial role in collisions.

●Kinetic Energy: Kinetic energy is the energy possessed by an object due to its
motion. During a collision, kinetic energy can be transferred between objects.

●Peak Force: Peak force refers to the maximum force exerted during a collision. It
represents the highest point of impact between the colliding objects.

●Deformation: Deformation refers to the change in shape of an object due to an
applied force during a collision. It can vary from microscopic to substantial and
permanent.

●Energy Transfer: Energy transfer occurs when energy moves from one object to
another during a collision. It is responsible for the change in energy distribution
between the colliding objects.

●Newton's Laws of Motion: Newton's Laws of Motion are fundamental laws that
describe the relationship between force, mass, and motion. They provide a framework
for understanding the behavior of objects during collisions.

Changes in Motion and Shape during
Collisions

Impact on Motion

During a collision, the motion of objects can change in terms of
speed, direction, or both. The collision can either increase or
decrease the objects' velocities, depending on the interaction
between them.

Impact on Shape

Collisions can also impact the shape of objects, particularly
those made of less rigid materials. The objects may bend, break,
or undergo other forms of deformation upon impact.

Open Ended

How can a collision impact an object's motion?

Force and Shape Changes in Collisions

Deformation in Every Collision

Every collision, regardless of its
magnitude, involves some
degree of deformation. Even for
rigid objects, there can be
microscopic and temporary
deformations. Less rigid objects,
however, can experience more
significant and permanent
changes in shape.

Visible and Non-visible
Changes

The changes in shape during a
collision can be both visible and
non-visible. Visible changes are
apparent, such as objects
breaking or bending. Non-visible
changes, on the other hand, may
involve microscopic alterations
that are not immediately
noticeable.

Open Ended

How does a collision impact and object's shape?

Relationship Between
Mass, Speed, and Kinetic
Energy

Increasing the mass or
speed of a moving object
before a collision results in
higher kinetic energy. The
kinetic energy determines
the magnitude of the
forces exerted during the
collision.

Greater Forces with
Increased Mass and
Speed

Objects with greater mass
and speed possess more
kinetic energy, leading to
stronger forces during
collisions. This can result
in more significant
damage or impact.

Impact of Mass and
Speed on Collisions

Multiple Choice

What is the relationship between mass and kinetic energy?

• Kinetic energy is inversely proportional to mass.
• Mass has no effect on kinetic energy.
• Kinetic energy is independent of mass.
• Kinetic energy is directly proportional to mass.

Multiple Choice

What is the relationship between kinetic energy and speed?

• Kinetic energy increases with the square of speed.
• Kinetic energy is independent of speed.
• Kinetic energy decreases with the square of speed.
• Kinetic energy is directly proportional to speed.

Multiple Choice

How does kinetic energy in a collision effect the amount of damage/deformation in the collision?

• Higher kinetic energy reduces damage and deformation.
• Higher kinetic energy in a collision increases the amount of damage and deformation.
• Kinetic energy has no effect on damage in a collision.
• Lower kinetic energy increases the amount of damage and deformation.

Role of Friction

and Air

Resistance in

Collisions

Opposing Forces that
Reduce Kinetic Energy

Friction and air
resistance are forces
that oppose motion. In
collisions, these forces
can dissipate some of
the kinetic energy,
reducing the overall
impact and potential
damage.

Use of Friction for
Vehicle Braking

In the context of
collisions, friction plays
a crucial role in vehicle
braking. By applying
friction between the
brake pads and the
wheels, the kinetic
energy of the moving
vehicle is gradually
reduced, allowing for
safer deceleration.

Multiple Choice

What is friction?

• Friction is the temperature increase caused by two surfaces rubbing together.
• Friction is the force that opposes the relative motion of two surfaces in contact.
• Friction is the force that enhances the motion of two surfaces in contact.
• Friction is the energy lost when two surfaces are in motion.

Real-World Examples of Collisions

Tennis Ball and Racket Collision: The collision between a tennis
ball and a racket showcases the transfer of energy and the
change in motion as the ball rebounds off the racket strings.
Car Crashing into a Wall: A car crashing into a wall
demonstrates the impact forces involved in a collision and the
potential damage caused to both the car and the wall.
Billiard Balls Colliding: The collision between billiard balls
illustrates the transfer of momentum and the resulting change in
motion as the balls change direction after impact.
Baseball Bat Striking a Baseball: When a baseball bat strikes a
baseball, the collision showcases the transfer of energy and the
resulting motion of the ball, potentially leading to a home run.
Egg Dropping and Cracking on the Floor: The collision of an
egg with the floor demonstrates the fragility of the eggshell and
the deformation that occurs upon impact, resulting in the
cracking of the egg.

Open Ended

Pick a real-world collision of your choice and explain the forces and energy transfer that occurs during the collision.

Conclusion

In conclusion, collisions involve the transfer of energy and
often result in changes in motion and shape.
Understanding the vocabulary related to collisions, the
impact of mass and speed, the role of friction and air
resistance, and real-world examples can provide valuable
insights into the dynamics of collisions and their effects
on objects.

Poll

Rate your overall understanding of collisions and the forces and energies that affect the collision.

• I still don't understand.

• I get some of it, but I'm still confused.

• I get it, but I need more practice and/or have some questions.

• I got this!