4 Momentum and Collisions Free Online FlashCards

How is linear momentum defined?

Linear momentum is mass times velocity: $\vec p=m\vec v$.

What determines the direction of an object's momentum?

Momentum is a vector, so it points in the same direction as the object's velocity.

What is the SI unit of momentum?

The SI unit of momentum is $\text{kg·m/s}$, equivalent to $\text{N·s}$.

What is the relationship between impulse and momentum change?

Impulse equals the change in momentum: $\vec J=\Delta\vec p=\vec p_f-\vec p_i$.

How is impulse calculated from average force?

For a constant or average force, $\vec J=\vec F_{\text{avg}}\Delta t$.

Why can airbags reduce the average force during a collision?

For the same momentum change, a longer stopping time means a smaller average force. Airbags and padding help by extending that time.

When is a system's total momentum conserved?

A system's total momentum remains constant when its net external impulse is zero or negligible during the interval considered.

Why don't internal collision forces change a system's total momentum?

Forces between objects within the system are internal and occur in equal-and-opposite pairs; they do not change the system's total momentum.

What momentum equation applies to a two-object, one-dimensional collision?

In one dimension, conserve momentum with consistent velocity signs: $m_1v_{1i}+m_2v_{2i}=m_1v_{1f}+m_2v_{2f}$.

Is momentum conserved in both elastic and inelastic collisions?

In an isolated system, total momentum is conserved in both elastic and inelastic collisions.

What quantities are conserved in an elastic collision?

An elastic collision conserves both total momentum and total kinetic energy.

What happens to kinetic energy in an inelastic collision?

An inelastic collision conserves total momentum, but some kinetic energy is transformed into other forms.