Mathematical and Physical Journal
for High Schools
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# Problem P. 4315. (February 2011)

P. 4315. Two balls of masses m1=0.173 kg and m2=0.2 kg are moving and the direction of their motion is perpendiculer to each other. Their speeds are v1=10 m/s and v2=5 m/s, respectively. After the collision the ball of mass m1 stops. What will the speed of the ball of mass m2 be after the collision?

(4 pont)

Deadline expired on March 10, 2011.

Sorry, the solution is available only in Hungarian. Google translation

Megoldás. Az ütközés előtt a két golyó együttes lendülete a merőleges haladási irány miatt $\displaystyle \sqrt{m_1^2v_1^2+m_2^2v_2^2}$. Az ütközés után a teljes lendületet a 2-es golyó viszi el, ezért ennek sebessége $\displaystyle v_2'=\sqrt{\left( \frac{m_1}{m_2} \right)^2v_1^2+v_2^2}\approx 10$ m/s.

### Statistics:

 171 students sent a solution. 4 points: 106 students. 3 points: 24 students. 2 points: 10 students. 1 point: 26 students. 0 point: 1 student. Unfair, not evaluated: 4 solutions.

Problems in Physics of KöMaL, February 2011