Find out also the loss of energy through impact, Mechanical Engineering

Find out also the loss of energy through impact:


1. A bullet weighing 0.1 newton horizontally fired with a velocity of 80 metres/sec hits a wooden block, weighing 0.9 Newton. This penetrates into the block through a distance of 8 cms while the latter is held firmly in a clamp. Find out the average resistance offered by the wooden block to the penetration of the bullet.

2. If the block were free to move on a smooth horizontal plane, find out the penetration of the bullet. Find out also the loss of energy through impact.


Consider the average resistance of wooden block to the penetration of the bullet be R Newtons.

 (i)        While block is held fixed in a clamp, the whole of Kinetic Energy (KE) of the bullet is lost in doing work of penetration of 8 cm (that means 0.08 metres).

∴ Work done by R = KE of bullet

R × 0.08 = (0.1 × 80 × 80) / (2 × 9.8)

∴ R = 408.16 N.

 (ii)       While the block is free to move horizontally, Consider Vc be the common velocity after impact

∴ (0.1 + 0.9) × Vc / g = (0.1 × 80) /g

∴ Vc  = 8 metres / sec .

Entire KE of the combined mass after impact

=  1 × 82 /2 × 9.8      = 3.27 N. m.                             ---------- (1)

Total KE of the system before impact

= (0.1 × 80 × 80 )/2 g   = 32.65 N-m-------------- (2)

∴ Energy lost in impact (i.e. in causing penetration)

                        = (1) - (2) = 29.38 N.m         ------------ (3)

Neglecting other losses like heat, sound etc. during the process of penetration, if we assume that resistance R absorbs this change in KE given in Eq. (3).

             R × l = 29.38

∴ l = 29.38 /408.16     = 0.072 m.

 Note down that penetration of 7.2 cm under case (ii) is less than that case (i).

N. B.    If the wooden block is free to move on a horizontal surface, it shall continue to move along a constant velocity Vc. Though, if R′ is a resistance offered so that it comes to rest through a distance s′, then

R′ × s′ = KE of the combined mass after the impact.

= 1 ×( Vc)2 / 2 g

Posted Date: 1/29/2013 7:04:54 AM | Location : United States

Related Discussions:- Find out also the loss of energy through impact, Assignment Help, Ask Question on Find out also the loss of energy through impact, Get Answer, Expert's Help, Find out also the loss of energy through impact Discussions

Write discussion on Find out also the loss of energy through impact
Your posts are moderated
Related Questions
Piston Area : The area of a circle of diameter equal to the cylinder bore is called the piston area and is designated by the letter A and is usually expressed in square centimetr

The Mechanical Engineer/Specialist shall prepare Material Requisitions for all required mechanical material and equipment. The format for all requisitions shall be in accordance w

(a) What are the functions of brake? What are the types of brakes? (b) How do brakes stop a moving vehicle? (c) What is the difference between brake and clutch? (d) Descri

TESTING OF RESISTANCE WELDS There are a number of destructive and non destructive tests available for testing the welds obtained by resistance welding. Radiographic or Ultrason

Motion of this particle: A particle of mass m is resting on a smooth horizontal plane as illustrated in Figure (a). It is associated to a spring which has a constant of k in f

Half-space Method Solid representation is based fundamentally on the notion that a physical object divides an n-dimensional space E n into two regions: interior and exterior,

Problem - Newton's Second Law in 2D A tow truck tows a 1000-kg car by applying a force of 1000 N north-northeast (67.5° above the x-axis).  a)  What are the components of th

a) Illustrate with the help of neat sketch any three straight line mechanism. b) Describe Degree of Freedom and prove the relation for Grumbler's equation.

why stress distribution diagram is different for I section, T section andcircular section?

WELD DEFECTS The common defects encountered in submerged arc welding are: a. Slag inclusion b. Porosity c. Cracking of welds.   a). Slag Inclusion : Slag in