Question

Two paper screens A and B are separated by a distance of 100 m. A bullet pierces A and then B. The hole in B is 10 cm below the hole in A. If the bullet is travelling horizontally at A, calculate the velocity of the bullet at A. Neglect the resistance of paper in air.

• A. 100 m/sec
• B. 400 m/sec
• C. 550 m/sec
• D. 700 m/sec

Answer 1

Answer: (D)

700 m/sec

Let the velocity at A be $u$
So , time taken to reach B = $\frac{100}{u}=t$
Now in this time, the height of the bullet will decrease by an amount
h = $\frac{1}{2}g{t}^2=10cm=0.1m$

So, putting the value of "t" from the previous equation and setting g = 9.8, we get
$u=700m/s$