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A stationary body of total mass M bursts into three fragments whose masses are in the ratio 1: 1: 2. The two lighter fragments move off at right angles to each other with speeds 30 m/s and 40 m/s. Find the speed of the heaviest fragment.

1. 15 m/s
2. 25 m/s
3. 35 m/s
4. 50 m/s

Correct answer: 25 m/s

Solution

The resultant momentum of the two small fragments is m*sqrt(30²+40²) = 50m, which must be balanced by the 2m fragment, giving its speed 25 m/s.

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