Abullet with a mass of 0.02 kg is fired horizontally into a block of wood hanging on a string. the bullet sricks in the wood and causes it to swing upward to a height of 0.2 m. if the mass of the wood block is 2 kg, what is the initial speed of the bullet?

u= 20.09 m/s

Explanation:

Given that

m = 0.02 kg

M= 2 kg

h= 0.2 m

Lets take initial speed of bullet = u m/s

The final speed of the system will be zero.

From energy conservation

1/2 m u²+ 0 = 0+ (m+M) g h

m u²=2 (m+M) g h

By putting the values

0.02 x u² = 2 (0.02+2) x 10 x 0.2       ( take g=10 m/s²)

u= 20.09 m/s