Question

Help Meeeeee
Two kids are roller skating. Amy, with a mass of 55 kg, is traveling forward at 3 m/s. Jenny, who has a mass of 40 kg, is traveling in the opposite direction at 5 m/s. They crash into each other and hold onto each other so that they move as one mass. How fast are they traveling?

Answer 1

Answer:

0.4 m/s

Explanation:

From the law of conservation of momentum, the sum of initial momentum equals the sum of final momentum

Momentum, p=mv where m is the mass and v is the velocity

$m_1v_1+m_2v_2=(m_1+m_2)v_c$ where $v_c$ is the common velocity, $v_1$ and $v_2$ are velocities of Amy and Jenny respectively, $m_1$ and $m_2$ are masses of Amy and Jenny respectively.

Taking forward direction as positive, opposite direction is negative hence $v_1$ is 3 m/s while $v_2=-5 m/s$

$55 kg\times 3 m/s +(40 kg\times -5 m/s)=(55 kg+40 kg)v_c$

$95 kg v_c=-35 kg.m/s$

$v_c=\frac {-35}{95}=-0.368421053  m/s\approx -0.4 m/s$

Therefore, they travel at 0.4 m/s in the direction of Jenny's movement