When a bullet with a mass of 10 g penetrates a board at a speed of 400 m / s and the speed becomes 100 m / s after passing through, the work done by the bullet to overcome the resistance is (1), If the thickness of the wood block is 10cm, the average resistance of the wood block to the bullet is (2) n. if the bullet can penetrate the cool wood block, the minimum velocity of the bullet is (3) m / s

The work a bullet does to overcome resistance
W=0.5mv1^2-0.5mv2^2=750j
If the thickness of the block is 10 cm, the average resistance of the board to the bullet is f
w=fd f=7500N
What is the minimum speed of a bullet to penetrate the same cool board
2 fd=0.5mv^2 v=547.7≈548m/s
The minimum velocity of a bullet is 548 M / s if it is to penetrate the same cool board

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