Question

A bullet of 10g strikes a sand bag at a speed of 10^3 m/sec and gets embedded after travelling 5cm.Calculate the resistive force exerted by the sand on the bullet??

Please answer according to Class 9 CBSE.

Answer 1

$\large \sf \underline{Solution - }$

Here it is given that,

• Mass of Bullet = 10g = 0.01kg
• Initial Velocity (u) = 1000m/s
• Distance covered (s) = 5cm = 0.05m
• Final Velocity (v) = 0m/s

We have to find,

• Force exerted by sand on bullet.

Formulae used,

• ➢ v² - u² = 2as
• ➢ F = ma

Now,

$\sf \implies \: {v}^2 - {u}^2 = 2as$

$\sf \implies \: 0^2 -1000 ^2= 2 \times a \times 0.05$

$\sf \implies \: -1000000 = 0.1 a$

$\sf \implies \: a = -10000000$

$\sf \implies \: a = -10 ^{7} \: m/s ^{2}$

➢ So, acceleration = - 10⁷m/s²

Therefore,

$\sf \implies \: F = ma$

$\sf \implies \: F = 0.01 \times - 10 ^{7}$

$\sf \implies \: \boxed{ \sf F = - 10 ^{5} N }$

So, The Force exerted by sand on bullet is - 10⁵N

➢ Note :- Negative Sign implies force is acting opposite to the Direction.