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A bullet loses 1/20 of its velocity in passing through a plank.The least number of planks needed to stop the bullet is...
one year ago

Arun
23370 Points

Dear Vaishnavi

Let the thickness of one plank = d

and the acceleration provided by the plank = a
If n planks are required to stop the bullet, then
0^2 = vo^2 + 2a*nd
2and = -vo^2
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
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

Regards

one year ago
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Course Features

• 110 Video Lectures
• Revision Notes
• Test paper with Video Solution
• Mind Map
• Study Planner
• NCERT Solutions
• Discussion Forum
• Previous Year Exam Questions