Question

A bullet of 10 g strikes a sand bag at a speed of 10^3 m/s and gets embedded after travelling 5 cm. Calculate: (in) the resistive force exerted by the sand on the bullet (ii) the time taken by the bullet to come to rest

Answer 1

Answer:

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i)10^5 N

ii)10^-4 s

Answer 2

Answer:

• (i) the resistive force exerted by the sand on the bullet is - 1 x 10⁵ N
• (ii) the time taken by the bullet to come to rest is 1 x 10⁻⁴ s

Given Parameter :

• mass of bullet, m = 10 g = 0.01 kg
• speed of the bullet, v = 1000 m/s = 10³ m/s
• distance traveled by the bullet, d = 5 cm = 0.05 m

Explanation:

(i) the resistive force exerted by the sand on the bullet

the acceleration of the bullet is given by;

→ v² = u² + 2as

→ 0 = (10³)² + a(2 x 0.05)

→ -0.1a = (10⁶)

→ -a = (10⁶) / 0.1

→ a = -1 x 10⁷ m/s²

The resistive force is given by;

➳ F = ma

➳F = (0.01)(-1 x 10⁷)

➳ F = - 1 x 10⁵ N

(ii) the time taken by the bullet to come to rest.

➝ v = u + at

➝ 0 = 10³ + (-1 x 10⁷ t)

➝ 1 x 10⁷ t = 10³

➝ t = 10³  / 10⁷

➝ t = 1 x 10⁻⁴ s