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I need help with these questions:


> A bullet is fired with an initial muzzle velocity of 500 ms^-1

a) Calculate the kinetic energy of the bullet if it has a mass of 20 grams.

b) The bullet penetrates a glass windows and is slowed down by 200 ms^-1. Calculate the residual kinetic energy and the energy that was used to break the glass.

c) What principle did you employ to calculate the energy that must have been used to break the glass?

Thank You.

2007-03-13 01:47:11 · 3 answers · asked by Anonymous in Science & Mathematics Physics

3 answers

a) E = 1/2 mv^2 = 1/2 20E-3kg x (500m/s)^2 = 2500 J

b) E = 1/2 mv^2 = 1/2 20E-3kg x (200m/s)^2 = 400 J
Energy to break the glass is 2500J - 400J = 2100J

c) Conservation of energy

2007-03-13 01:56:59 · answer #1 · answered by catarthur 6 · 0 0

Kinetic Energy = 0.5 x mass x the square of velocity

a: 0.5 x 0.02 (kg) x 500^2 m/s = 2,500 J

b: 0.5 x 0.02 x 300^2 = 900 J (residual KE) --> 2,500-9000 = 1,600 J (Energy to break glass)

c: Conservation of Energy

2007-03-13 02:17:30 · answer #2 · answered by Anonymous · 0 0

calculate how much time it took the bullet to get to the glass and multiply it by the velocity. Then divide it by the bullets mass. Subtract that number from 200 ms^-1 and there is ur anser.

2007-03-13 01:52:58 · answer #3 · answered by baadgurl 1 · 0 1

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