Question

Kevin has a mass of 87 kg and is skating with in-line skates. He sees his 22-kg younger brother up ahead standing on the sidewalk, with his back turned. Coming up from behind, he grabs his brother and rolls off at a speed of 2.4 m/s. Ignoring friction, find Kevin’s speed just before he grabbed his brother.

Answer 1

Answer:

$V_ k = 3 m/s$  

Explanation:

Using the conservation of the linear momentum P:

$P_i = P_f$

so:

$M_kV_k = M_sV_s$

where $M_k$ is the mass of kevin, $V_k$ is the velocity of kevin before he grabs her brother, $M_s$ is the velocity of her brother and him after grabs her brother and $V_s$ is the velocity of both after the collition.

So, replacing the values and solving for Vk, we get:

$(87 kg)V_k = (87 kg+22 kg)(2.4m/s)$

$V_ k = 3 m/s$