Question

Q7.a bullet of 100g strikes a sand bag at speed of 1000m/s and get embedded after travelling 5 cm . calculate the resistive force exerted by the sand on the bullet

Answer 1

Answer :

Mass of bullet = 100g = 0.1kg

Initial speed = 1000m/s

Distance covered by bullet = 5cm = 0.05m

We have to find resistive force exerted by the sand on the bullet$.$

★ In order to find force exerted by the sand, first we need to find acceleration of bullet.

Using third equation of kinematics :

• v² - u² = 2as

v denotes final speed

u denotes initial speed

a denotes acceleration

s denotes distance

Here final speed of bullet will be zero as it comes to rest.

➝ 0² - (1000)² = 2(a)(0.05)

➝ -1,000,000 = 0.1a

➝ a = -10,000,000 m/s²

Negative sign shows retardation!

We know that,

• Force = Mass × Acceleration

➝ F = m × a

➝ F = 0.1 × 10,000,000

➝ F = 1,000 kN