Home
Class 11
PHYSICS
A bullet leaving the muzzle of a rifle b...

A bullet leaving the muzzle of a rifle barrel with a velocity v penetrates a plank and loses one-fifth of its velocity. It then strikes second plank, which it just penetrates through. Find the ratio of the thickness of the planks, supposing the average resistance to the penetration is same in both the cases.

Text Solution

Verified by Experts

Let R be the resistance force offered by the planks, `t_1` be the thickness of first plank, and `t_2` be the thickness of second plank.
For first plank:
Loss in KE=work against resistance
`1/2mv^2-1/2m(4/5v)^2=Rtimplies1/2mv^2(9/25)=Rt_1` (i)
For second plank:
`1/2m(4/5v)^2-0=Rt_2implies1/2mv^2(16/25)=Rt_2` (ii)
Dividing Eq. (i) by Eq. (ii), we get `t_1/t_2=9/16`
Promotional Banner

Topper's Solved these Questions

  • WORK, POWER & ENERGY

    CENGAGE PHYSICS|Exercise Solved Examples|15 Videos

  • WORK, POWER & ENERGY

    CENGAGE PHYSICS|Exercise Exercise 8.1|25 Videos

  • VECTORS

    CENGAGE PHYSICS|Exercise Exercise Multiple Correct|5 Videos

Similar Questions

Explore conceptually related problems

A bullet passes through a plank and loses (1)/(20) of its initial velocity. The minimum number of such planks which can just stop the bullet is

A bullet moving with a speed 'v' can just penetrate two planks of equal thickness. Number of such planks that the bullet will penetrate if its speed is doubled, is:

Having gone through a plank of thickness h, a bullet changed its velocity from v_(0) to v_(1) . Find the time of motion of the bullet on the plank, assuming the resistance force to be proportional to the square of the velocity.

A bullet loses 1//2th1 of its velocity is passing through a plank. What is the least number of planks required to stop the bullet ?

A bullet is fired at a target with a velocity v. It is found that its velocity decreases from v to v//2 when it penetrates 30 cm in the target. Through what thickness it will penetrate further in the targer, before coming to rest?