Question

A wooden block of mass 10 gm is dropped from the top of a tower 100 m high. Simultaneously, a bullet of mass 10 gm is fired from the foot of the tower vertically upwards with a velocity of 100 m/s. If the bullet is embedded in it, how high will it rise above the tower before it starts falling? (g = 10 m/s²⁾

• A. 80 m
• B. 85 m
• C. 75 m
• D. 10 m

Answer 1

Answer: (C)

75 m

Answer 2

Block and bullet will collide after 1 sec at height 95 m from ground.

Velocity of block before collision = gt = 10 m/s

Velocity of bullet before collision=u–gt=90 m/s

from conservation of linear momentum,

m(–10) + m(90) = 2 mv' Ž v' = 40 m/s

Thus height raised by the combined mass

h = $\frac { 40 \times 40 } { 2 \times 10 }$ = 80 m

height from tower = 75 mW