183_notes:examples:momentumslow [Projects & Practices in Physics]

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====== Example: Calculating the momentum of a slow-moving object ======

A [[http://s.hswstatic.com/gif/1971-1980-ford-pinto-1971.jpg|1971 Ford Pinto]] is observed to moving with a velocity of $\langle 22.35, 0, 1.06\rangle\dfrac{m}{s}$. Determine the momentum of this sweet ride.

==== Setup ====

You need to compute the momentum of a 1971 Ford Pinto using the information provided and any information that you can collect or assume.

=== Facts ====

  * The Ford Pinto is in motion
  * It has a velocity, $\vec{v}_{car} = \langle 22.35, 0, 1.06\rangle\dfrac{m}{s}$.
  
=== Lacking ===

  * The mass of the Ford Pinto is not given, but can be [[http://lmgtfy.com/?q=mass+of+a+1971+ford+pinto+sedan|found online]] ($m_{car} = 884.05 kg$).

=== Approximations & Assumptions ===

  * The Ford Pinto experiences several forces, but over the short time we are looking at it, it experiences no net force, so its velocity will remain unchanged.
  * The velocity of the Ford Pinto is much less than the speed of light ($|\vec{v}_{car}| \ll c = 3.00\times10^8 \dfrac{m}{s}$).


=== Representations ===

  * The momentum of the Ford Pinto is given by $\vec{p} = m \vec{v}$.

==== Solution ====

We compute the momentum vector.

$$\vec{p}_{car} = m_{car} \vec{v}_{car} = (884.05 kg) \langle 22.35, 0, 1.06\rangle\dfrac{m}{s} = \langle 1.98 \times 10^4, 0, 9.37 \times 10^2\rangle \dfrac{kg\:m}{s}$$