6. A `5000`-`kg` boxcar traveling at `18.0\ m//s` strikes a second `4000`-`kg` boxcar at rest. The two cars stick together after the collision. What is the speed of the two cars after collision?
6. A 5000-kg boxcar traveling at 18.0\ m//s strikes a second 4000-kg boxcar at rest. The two cars stick together after the collision. What is the speed of the two cars after collision? `p_i = p_f`
`v_f = 10.0\ m//s`
Given:
`m_1 = 5000\ kg`
`v_(1_i)=18.0\ m//s`
`m_2= 4000\ kg`
Equations:
`p_i = p_f`
Solution:
`p_i = p_f`
`=>`
`m_1 v_(1_i) + m_2 v_(2_i) = m_1 v_(1_f) + m_2 v_(2_f)`
From the given values `=>`
`m_1 v_(1_i) + 0 = m_1 v_f + m_2 v_f`
`=>`
`m_1 v_(1_i) = (m_1 + m_2) v_f`
`v_f =m_1/(m_1 + m_2) v_(1_i)`
`v_f =(5000\ kg) /((5000\ kg)+(4000\ kg)) (18.0\ m//s)`
`v_f = 10.0\ m//s`
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