A car with a mass of 1300kg travels at 2.0 m/s and bumps into a stopped car with a mass of 1300 kg. After the collision, the two cars stick together and move forward. How fast will they both move forward?

1 answer

To solve this problem, we can use the principle of conservation of momentum. The total momentum before the collision must equal the total momentum after the collision.

  1. Calculate the initial momentum of the system:

    The initial momentum \( p_{\text{initial}} \) can be calculated using the formula: \[ p_{\text{initial}} = m_1 v_1 + m_2 v_2 \] where:

    • \( m_1 = 1300 , \text{kg} \) (mass of the moving car)
    • \( v_1 = 2.0 , \text{m/s} \) (velocity of the moving car)
    • \( m_2 = 1300 , \text{kg} \) (mass of the stopped car)
    • \( v_2 = 0 , \text{m/s} \) (velocity of the stopped car)

    Plugging in the values: \[ p_{\text{initial}} = (1300 , \text{kg})(2.0 , \text{m/s}) + (1300 , \text{kg})(0 , \text{m/s}) = 2600 , \text{kg m/s} \]

  2. Calculate the final momentum of the system after the collision:

    After the collision, the two cars stick together. Let \( v_f \) be the final velocity of the combined mass after the collision. The total mass after the collision is: \[ m_{\text{total}} = m_1 + m_2 = 1300 , \text{kg} + 1300 , \text{kg} = 2600 , \text{kg} \]

    The momentum after the collision \( p_{\text{final}} \) can be expressed as: \[ p_{\text{final}} = m_{\text{total}} v_f = 2600 , \text{kg} v_f \]

  3. Set the initial momentum equal to the final momentum:

    According to the conservation of momentum: \[ p_{\text{initial}} = p_{\text{final}} \] Substituting the known values: \[ 2600 , \text{kg m/s} = 2600 , \text{kg} v_f \]

  4. Solve for \( v_f \):

    \[ v_f = \frac{2600 , \text{kg m/s}}{2600 , \text{kg}} = 1.0 , \text{m/s} \]

Thus, after the collision, both cars will move forward together at a velocity of 1.0 m/s.