Question

can anyone plzz tell me these numerical fast plzz

Answer 1

Acceleration of bullet
a = (v² - u²) / (2S)
= (0 - (400 m/s)²) / (2 × 0.1 m)
= -8 × 10⁵ m/s²

Force exerted by wall on bullet
F = ma
= (30 × 10⁻³ kg × -8 × 10⁵ m/s²)
= -24000 N

(Negative sign indicates that Force is in the direction opposite to that of velocity of bullet. If we consider velocity of bullet to be -400 m/s then force exerted by wall on bullet would have been +24000 N).

Answer 2

Mass of bullet(m)= 30g = 0.03kg.
Initial velocity (u)= 400m/s.
Final velocity (v)= 0m/s. [Since bullet comes to rest after penetrating 10 cm in wall]
Distance penetrated by bullet (S) or displacement of bullet in presence of resistive force = 10 cm = 0.1m.
Acceleration (a)=?
From third equation of motion:
v^2=u^2+2aS
0^2= 400^2+2a*0.1
0.2a=-160000
a=-160000/0.2= -8,00,000m/s^2.
The negative sign shows that acceleration takes place in direction opposite to the initial direction of motion of bullet or retardation takes place.
Avg. force (f)= m*a
f= 0.03*-800000
f= -24000N
Here too negative sign shows that force applied by mud wall on bullet is in direction opposite to initial direction of motion of bullet.