Mathematical and Physical Journal
for High Schools
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Problem P. 4029. (December 2007)

P. 4029. A 2 kg body, moving on a frictionless horizontal track, reaches another object of 3 kg made of the same material, moving in front of the 2-kg object, and collides with it totally inelastically. Their common speed after the collision is 4 m/s. Due to the collision the temperature of the two objects, which was initially the same, is increased, though only by 0.006 oC. The specific heat capacities of the two objects are the same: 0.5~\frac{\rm kJ}{\rm kg\cdot {}^\circ\rm C}.

a) What were the initial speeds of the colliding objects before the collision?

b) What percent of the initial kinetic energy is transferred to increase of the internal energy of the two objects?

(4 pont)

Deadline expired on January 11, 2008.


201 students sent a solution.
4 points:130 students.
3 points:29 students.
2 points:25 students.
1 point:4 students.
0 point:1 student.
Unfair, not evaluated:12 solutions.

Problems in Physics of KöMaL, December 2007