Impulse and Automobile Design

Recap of Work and Energy

  • Energy: Capacity to do work; measured in joules.

  • Work: Defined as force applied over a distance, also measured in joules.

Conservation of Energy

  • Law of Conservation of Energy: Energy cannot be created or destroyed, only transformed from one form to another.

    • Common transformations include chemical energy to mechanical energy, etc.

    • Key types: Kinetic Energy and Potential Energy.

Kinetic Energy

  • Definition: Energy due to the motion of an object.

  • Formula: KE = ( \frac{1}{2} mv^2 )

    • Importance of the squared term: Kinetic energy increases significantly as velocity increases.

Potential Energy

  • Definition: Energy due to an object's position.

    • Example: Roller coaster starts at height, converting potential energy to kinetic energy as it descends, gaining speed while losing height.

Power

  • Definition: The rate at which work is done; measured in watts.

  • Implication: Performing work quicker requires more power.

Work-Energy Principle

  • Principle: Net work done on an object equals the change in its kinetic energy.

  • Significance in physics: Crucial for understanding impacts and collisions.

Momentum

  • Definition: Product of an object's mass and velocity; represented by ( p ).

    • Remarkable facts:

    • High momentum from a small object at high speed or a large object moving slowly.

  • Calculation Example:

    • Bullet example: 15 grams traveling at 380 m/s.

    • Remember to convert grams to kilograms (15g = 0.015 kg).

Conservation of Momentum

  • In a closed system, total momentum remains constant:

    • Formula for interactions: ( m_1 u_1 + m_2 u_2 = m_1 v_1 + m_2 v_2 )

    • Real-world applications: Vital in analyzing collisions.

Types of Collisions

Elastic Collisions

  • Definition: Both momentum and kinetic energy are conserved.

    • Example: A rubber ball bouncing off another.

Inelastic Collisions

  • Definition: Momentum is conserved, but kinetic energy is lost to deformation or heat.

    • Example: Car crash where vehicles don’t rebound but deform.

Redistribution of Momentum in Car Crashes

  • Momentum conservation principles applied to car collisions:

    • Example of a Honda model demonstrating energy release and vehicle deformation.

Impulse

  • A force acting on an object in a period creating a change in momentum

  • F-mΔv/Δt= Δp

Car Safety Elements

  • Crumple zones: Designed to absorb energy during impact, increasing INTERACTION TIME, hence decreasing the force experienced by passengers.

  • Airbags: Disperse forces over a larger area that is exerted by the steering wheel; crucial in reducing impact severity. this is shown by increasing TIME INTERVAL over the force applied

    • There is also a SIPS feature since the brain is more sensitive to impacts on the side or the back

  • Collapsable steering column: Reduces injuries towards the chest and sternum (flail chest) that is caused by rigid steering wheels. Its job is to absorb IMPACT ENERGY and increase INTERACTION TIME

  • Padded interiors: Reduces IMPACT FORCE by increasing INTERACTION TIME.

Seatbelts

  • Types:

    • Lap sash belts: Can cause internal injuries.

    • 3-point seat belts: More effective in spreading force and preventing movement.

    • Inertia reel seatbelts: Lock upon sudden movement, allowing more comfort during normal driving.

  • The significance of seat belts: They prevent ejection from the vehicle and reduce impact forces on the occupant's body. Increasing SOPPING DISTANCE

  • Preassue is a factor that goes across the lap and chest in the formula P=F/A preventing from contacting the glass.