Question

A bullets of mass 10 g is fired rifle with a speed of 800 m/s. After passing through a mud wall 1m thick the speed drops to 200m,/s. Calculate the work done

Answer 1

Initial speed = u = 800m/s
Final speed = v = 200m/s
Mass of bullet = 10g = 0.01 kg
Distance travelled = 1 m
Acceleration = a

v² - u² = 2 × a × s
(200)² - (800)² = 2a(1)
40000 - 640000 = 2a
- 600000 = 2a

so a = - 300000 m/s²
Work done = F.s
= m×a×s
= 0.01×(-300000)×1
= - 3000 J
So work done by the bullet is 3000 J
but work done by the wall is - 3000 J

Answer 2

Answer:

-3000 J

Explanation:

Initial. velocity =800 m/s

final velocity = 200m/s

mass =0.01 kg

work done =1/2mv^2-1/2mu^2

( 1/2*0.01*800*800) -1/2*0.01*200*200)

-3000 J