How Fast Was Kevin Skating Before the Inelastic Collision?

AI Thread Summary
To determine Kevin's speed before the collision with his brother, apply the principle of conservation of momentum, as kinetic energy is not conserved in inelastic collisions. The total momentum before the collision must equal the total momentum after the collision. Given Kevin's mass of 84.2 kg and his brother's mass of 23.2 kg, along with their combined speed of 1.74 m/s after the collision, the equation can be set up to solve for Kevin's initial speed. The discussion emphasizes the importance of using momentum conservation rather than kinetic energy for this type of problem. Understanding these concepts is crucial for solving similar physics problems effectively.
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Homework Statement


Kevin has a mass of 84.2 kg and is skating with in-line skates. He sees his 23.2-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 1.74m/s. Ignoring friction, find Kevin's speed just before he grabbed his brother.


Homework Equations


V= d/t ?
I have no idea how to solve this eqn!
The only eqn i have for perfectly inelastic collision involves center of mass.

PLEASE HELP!
 
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agadag said:

Homework Statement


Kevin has a mass of 84.2 kg and is skating with in-line skates. He sees his 23.2-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 1.74m/s. Ignoring friction, find Kevin's speed just before he grabbed his brother.


Homework Equations


V= d/t ?
I have no idea how to solve this eqn!
The only eqn i have for perfectly inelastic collision involves center of mass.

PLEASE HELP!

In an inelastic collision, kinetic energy is lost, but momentum is still conserved. Use conservation of momentum.
 

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