AP Physics 1 elastic vs inelastic collisions key terms

Define elastic collision.

An elastic collision is a type of collision where both momentum and kinetic energy are conserved.

True or False: Kinetic energy is not conserved in elastic collisions.

False. Kinetic energy is conserved in elastic collisions, unlike inelastic collisions.

What quantities are conserved in elastic collisions?

Momentum and kinetic energy are both conserved.

Fill in the blank: In elastic collisions, the relative velocity before and after the collision is ____.

equal in magnitude and opposite in direction.

Compare elastic and inelastic collisions.

- Elastic: KE and momentum conserved. - Inelastic: KE not conserved, momentum conserved.

What is the formula for kinetic energy?

$\displaystyle KE = \\frac{1}{2} mv^2$ where m is mass and v is velocity.

Give an example of an elastic collision.

Two billiard balls colliding is an example where both momentum and kinetic energy are conserved.

Calculate the final velocities in a 1D elastic collision.

$\displaystyle v_{1f} = \\frac{(m_1 - m_2)v_{1i} + 2m_2v_{2i}}{m_1 + m_2}$, $\displaystyle v_{2f} = \\frac{(m_2 - m_1)v_{2i} + 2m_1v_{1i}}{m_1 + m_2}$.

True or False: Elastic collisions can occur at any speed.

True. Elastic collisions can happen at low or high speeds, provided the conditions allow for KE conservation.

Describe the ideal conditions for elastic collisions.

Ideal conditions include no external forces, perfectly rigid bodies, and no energy loss.

What happens to total kinetic energy in elastic collisions?

Total kinetic energy remains constant before and after the collision.

What types of objects typically undergo elastic collisions?

Objects like gas molecules and hard spheres (e.g., billiard balls) often undergo elastic collisions.

Fill in the blank: The coefficient of restitution for elastic collisions is ____.

equal to 1.

List the steps to analyze an elastic collision.

- Identify masses. - Set up conservation equations. - Solve for unknowns.

Explain what is meant by the term 'perfectly elastic'.

Perfectly elastic indicates no loss of kinetic energy; all energy is transformed back into kinetic after collision.

What is a key characteristic of elastic collisions in one dimension?

The final velocities can be directly calculated using conservation laws and specific formulas.

Define an inelastic collision.

An inelastic collision is one where kinetic energy is not conserved, although momentum is conserved.

True or False: Kinetic energy is conserved in inelastic collisions.

False. Kinetic energy is not conserved in inelastic collisions due to deformation and heat.

Fill in the blank: In an inelastic collision, the objects ____ after the collision.

stick together or move as one mass.

What happens to momentum in inelastic collisions?

Momentum is conserved, regardless of the kinetic energy changes.

Give an example of an inelastic collision.

A car crash where the cars crumple and move together.

What is a perfectly inelastic collision?

A perfectly inelastic collision is one in which the colliding objects stick together after the collision.

Compare elastic and inelastic collisions.

Elastic: KE conserved, objects bounce. Inelastic: KE not conserved, objects stick.

Cause → Effect: High-speed crash results.

Result: Significant deformation, energy loss, heat generation.

Calculate: Two cars collide with masses 1000 kg and 2000 kg, velocities 10 m/s and -5 m/s.

Final velocity = \( v_f = \\frac{(1000 \cdot 10) + (2000 \cdot (-5))}{1000 + 2000} = \\frac{10000 - 10000}{3000} = 0 \) m/s.

Does energy change in inelastic collisions?

Yes, mechanical energy is transformed into other forms such as heat and sound.

True or False: Momentum can change in inelastic collisions.

False. Momentum is conserved in inelastic collisions.

What is the coefficient of restitution in inelastic collisions?

The coefficient of restitution is less than 1, indicating energy loss.

Describe the energy transformation in inelastic collisions.

Kinetic energy is converted into heat, sound, and potential energy due to deformation.

What does the symbol \( p \) represent?

The symbol \( p \) represents momentum, calculated as \( p = mv \) (mass times velocity).

In inelastic collisions, what happens to total energy?

Total energy is conserved, but kinetic energy is transformed into other forms.

Name one real-life application of inelastic collisions.

Automobile safety features like crumple zones use inelastic collisions to absorb impact.

What does conservation of momentum state?

The total momentum of a closed system remains constant before and after a collision.

True or False: Inelastic collisions conserve kinetic energy.

False. Inelastic collisions do not conserve kinetic energy, some is transformed into other forms.

Define closed system in the context of collisions.

A closed system is one where no external forces act on the objects involved, allowing total momentum to be conserved.

Fill in the blank: In a perfectly elastic collision, _____ is conserved.

kinetic energy and momentum.

How do elastic and inelastic collisions differ in energy conservation?

- Elastic: Kinetic energy conserved. - Inelastic: Kinetic energy not conserved.

Calculate the total momentum: m1=2 kg, v1=3 m/s; m2=3 kg, v2=1 m/s.

Total momentum: $\displaystyle p_{total} = m_1 v_1 + m_2 v_2 = (2 imes 3) + (3 imes 1) = 6 + 3 = 9 ext{ kg m/s}$.

Cause → Effect: If two objects collide elastically, what occurs?

Both momentum and kinetic energy are conserved.

What is the formula for momentum?

Momentum ($\displaystyle p$) is given by: $\displaystyle p = mv$, where $\displaystyle m$ is mass and $\displaystyle v$ is velocity.

True or False: Momentum can change in a closed system.

False. In a closed system, momentum remains constant.

What happens to energy in a totally inelastic collision?

Some kinetic energy is transformed into sound, heat, or deformation energy.

Compare momentum conservation in elastic vs inelastic collisions.

- Both conserve momentum. - Only elastic collisions conserve kinetic energy.

What is an example of a real-world elastic collision?

Billiard balls colliding on a table, where they bounce off without losing speed.

What happens during a car crash?

Inelastic collision occurs; momentum conserved. Kinetic energy is not conserved, resulting in deformation.

Example of elastic collision in sports?

Pool balls colliding; they bounce off each other, conserving kinetic energy and momentum.

True or false: A train colliding with a car is elastic.

False. It's inelastic; the train continues moving while the car crumples.

Fill in the blank: A rubber ball bouncing back after hitting the floor is an __________ collision.

elastic

Cause of airbags in cars?

Reduce impact force during collisions—minimize injury. They inflate quickly, preventing inelastic collision injuries.

Compare elastic and inelastic collisions in terms of energy.

Elastic: kinetic energy conserved. Inelastic: kinetic energy not conserved; transformed into other forms.

What is a real-world example of inelastic collision?

Car accidents: vehicles stick together or crumple upon impact, conserving momentum but losing kinetic energy.

How does a football tackle illustrate inelastic collisions?

Players collide, momentum is conserved, but kinetic energy is lost to sound, heat, and deformation.

Example of momentum conservation in sports?

A soccer ball being kicked; player imparts momentum, ball travels, both player and ball have momentum before and after.

True or false: Bumper cars are an example of elastic collision.

False. They are inelastic; cars bump, move apart, energy is lost in sound and deformation.

Real-world application of collision theory in safety?

Crash tests for vehicles; understanding collisions helps improve designs for safety.

What type of collision is a meteor entering Earth's atmosphere?

Inelastic; it loses kinetic energy due to heat and pressure, creating a high-energy impact.