Question

1 20 3 Diagram is snapshot before collision. Mass of each boxcar = 10,000 kg.

Refer to the illustration of three boxcars, above.

65. The Boxcar 1 moves to the right at speed v₁ = 5.4 m/s. Boxcars 2 and 3 are initially at rest. The total momentum before interaction is

A. 63000 kg m/s

B. 198450 kg m²/s²

C. 189000 kg m/s

D. 54000 kg m/s

66. The Boxcar 1 moves to the right at speed v₁ = 5.4 m/s. After collision, the three boxcars latch together and move off together as one mass, with speed v_new to the right. The new speed v_new is...

A. 3.6 m/s

B. 1.8 m/s

C. 2.1 m/s

D. 122 m/s

Answer 1

65. momentum before collision:

$\Rightarrow p = 10000\times5.4=54000 \hspace{.3cm}kg-m/s$

option D.

66. Applying momentum conservation.

$\Rightarrow p_i = p_f$

$\Rightarrow 54000 = 30000\times v_{new}$

$\Rightarrow v_{new}=\frac{54000}{30000}=1.8\hspace{.3mm}m/s$

option B.