Question

the velocity of a bullet is reduced from 200m/s to 100m/s while traveling through a wooden block of thickness 10cm the retardation, assuming it to be uniform, will be

Answer 1

By using 2as=v^2 -u^2we haveu=200m/s v=100m/s& s=0.1m(10cm) from here deacc ( retardation)comes 150000m/s

Answer 2

Given,

Initial velocity ( u )= 200 m/s 

Final velocity ( v )= 100 m/s

Distance traveled ( s ) = 10 cm = 0.1 m.

Uniform retardation ( a )  = ?


Using equation of motion ,

⇒ v² = u² + 2 as

⇒ ( 100 m/s )² = ( 200 m/s )² + 2 a ( 0.1 m )

⇒ ( 100 m/s )² - ( 200 m/s )² = 2 a ( 0.1 m ) 

⇒ ( 100 m/s + 200 m/s ) ( 100 m/s - 200 m/s ) = 2 a ( 0.1 m )

⇒ ( 300 m/s ) ( - 100 m/s ) = 2 a ( 0.1 m )

⇒ ( - 30,000 m² /s² ) = 2 a ( 0.1 m )

⇒ ( - 30,000 m² ) / ( s² × 2 × 0.1 m ) = a

⇒ ( - 3,00,000 m² ) / ( s² × 2 × m ) = a

⇒ - 1,50,000 m / s² = a

∴ Uniform retardation  = 1,50,000 m / s².