Question

the momtumom of a bullet of mass 20 gm is 16 kg m/s the kinetic energy of this bullet will be

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Answer 1

Answer:

The mass of bullet is 20 g or 0.02 kg.

The momentum of the bullet is 10 kg⋅m/s

The kinetic energy of a body in terms of its momentum is given as:

KE=

2m

KE=

2×0.02

10×10

2500 J= 2.5 kJ

Answer 2

• Momentum of the bullet, p = 16 kgm/s

• Mass of the bullet, m = 20 gram.

$1 \: g \: = {10}^{ - 3} \: kg \\ \\ 20\: g \: = 20 \times {10}^{ - 3} \: kg \\ \\ m = 2 \times {10}^{ - 2} kg$

We know that,

Momentum, p = m× v

where v is the velocity of the bullet.

$16 = 2 \times {10}^{ - 2} \times v \\ \\ v = \dfrac{16}{2 \times {10}^{ - 2} } \\ \\ v = \dfrac{16 \times {10}^{2} }{2} \\ \\ v = 8 \times {10}^{2} \: \frac{m}{s}$

Velocity of the bullet, v = 8 × 10² m/s.

Let k be the kinetic energy of the bullet.

Kinetic energy,

$k = \dfrac{1}{2} m {v}^{2} \\ \\ = \frac{1}{2} \times 2 \times {10}^{ - 2} \times {(8 \times {10}^{2}) }^{2} \\ \\ = {10}^{ - 2} \times 8 \times 8 \times {10}^{4} \\ \\ = 64 \times {10}^{ (- 2 + 4)} \\ \\ k= 64 \times {10}^{2} \: joules \\ \\ = 64 \times 100 \\ \\ k= 6400 \: joules$

Kinetic energy of the bullet is 64×10² J or 6400 J.