Use Coupon: CART20 and get 20% off on all online Study Material

Total Price: Rs.

There are no items in this cart.
Continue Shopping
Mohammed faisal anees Grade: 11

A bullet loses 1/20 of its velocity after penetrating into a plank. How many planks are required to stop the bullet ?

7 years ago

Answers : (3)

Prudhvi teja
83 Points

Dear mohammod

Let the thickness of one plank = d
and the acceleration provided by the plank = a

v^2 = vo^2 + 2ad
If n planks are required to stop the bullet, then
0^2 = vo^2 + 2a*nd
2and = -vo^2
n = vo^2/(-2ad) -----------------(1)

v = vo - vo/20 = 19 vo/20 in passing through one plank
(19 vo/20)^2 = vo^2 + 2ad
361/400 * vo^2 = vo^2 + 2ad
-2ad = vo^2(1 - 361/400)
-2ad = vo^2 * 39/400

Substituting this value of -2ad into equation (1):
n = vo^2/(vo^2 * 39/400) = 400/39
The minimum number of planks needed = smallest integer greater than 400/39 = 11
Ans: 11


Please feel free to post as many doubts on our discussion forum as you can.we will get you the answer and detailed  solution very  quickly.

All the best.

Askiitians Experts
Prudhvi Teja



Now you can win exciting gifts by answering the questions on Discussion Forum. So help discuss any query on askiitians forum and become an Elite Expert League askiitian

7 years ago
vikas askiitian expert
510 Points

applying v^2=u^2+2ad  ,here d is the width of plank

 v=u/20 after penetrating 0ne plank

  2ad=399u^2/400 .........eq1 

  for n number of planks total distance after which bullet stops is nd

 again applying v^2=u^2+2adn  and putting v=0


 solving 1and 2 


7 years ago
17 Points
										The formula is m=n^2÷2n-1Substituting in this we will be getting 400÷39So the answer should be approximately 10Therefore the required number of planks is 10....
5 months ago
Think You Can Provide A Better Answer ?
Answer & Earn Cool Goodies
  • Complete JEE Main/Advanced Course and Test Series
  • OFFERED PRICE: Rs. 15,900
  • View Details
  • Kinematics & Rotational Motion
  • OFFERED PRICE: Rs. 636
  • View Details

Ask Experts

Have any Question? Ask Experts

Post Question

Answer ‘n’ Earn
Attractive Gift
To Win!!! Click Here for details