Question

. A bullet of mass 100 g hits a block of thickness
5 cm with a speed of 200 m/s. It emerges with
10% of its initial kinetic energy. Then, its emergent
speed will be
[NCERT Pg. 125]
(1) 20
$\sqrt{10}$

(2) 2013 m/s
(3) 20 m/s
(4) 10/10 m/s​

Answer 1

Answer:

(1) 20√10

Explanation:

see the attached image

Answer 2

Answer:

The emergent speed is- $20\sqrt{10}$ m/s which is option number 1.

Explanation:

• We are asked to find the emergent speed that is v.
• We are also given with some information, such as-

There is a bullet of mass 100 g.

This bullet hits one block, and the thickness of that block is 5cm.

The bullet hits the block with the speed of 200m/s.

The emerges that is initial energy which is kinetic energy is 10%.

Lets write them is symbolic form-

m= 100g that is 0.1 kg. u= 200m/s

We know that-

$K.E=\frac{1}{2} \times mu^{2}$

Putting the values-

$\frac{1}{2}\times 0.1\times200^{2} \\\frac{1}{2}\times 4000\\ K.E= 2000J$

We are given that-

$K.E (final)=\frac{10}{100}$

Since,

$K.E(final)= \frac{1}{2}mv^{2} \\K.E(final)= \frac{1}{2}\times 0.1\times v^{2} \\\\\\200=\frac{1}{2}\times0.1\times v^{2} \\4000=v^{2} \\v= 20\sqrt{10}m/s$

Hence, the emergent speed will be 20 root 10 m/s

#SPJ2

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