Question

How fast would a(n) 75 kg man need to run in order to have the same kinetic energy as an 8.0 g bullet fired at 420 m/s ?

Answer 1

• Mass of the bullet (m1) = 8g = 0.008 Kg
• Velocity of the bullet (v1) = 420 m/s
• We know, kinetic energy =
  `(1)/(2)m {v}^(2)`
• Therefore, the kinetic energy of the bullet

`= (1)/(2) * 0.008 * 420J \\ = 1.68J`

• So, the kinetic energy of the bullet is 1.68 J. It is said that the man's kinetic energy should be same as that of the bullet.
• Mass of the man (m2) = 75 Kg
• Let the velocity of the man be v2.
• Therefore,

`1.68J = (1)/(2) * 75 \: kg * v2 \\ = > v2 = (1.68 * 2)/(75) m {s}^( - 1) \\ = 0.0448 \: m \: {s}^( - 1)`

Answer:

0.0448 m/s

Hope you could get an idea from here.

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