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

Find out also the loss of energy through impact:

Example

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.

Solution

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
(a) A spring mass system has a period 0.25 sec. What will be the new period if spring constant is increased by 50% ? (b) A vibratory system in a vehicle is to be prepared with t

Explain Soft or Flexible Automation? This system uses tape, a hand-held control box, microprocessors, programmable logic controllers or computers. The system can be reprogramme

Nozzle: The pressure energy gets converted in to kinetic energy Mass flow rate  Turbine: It is used to generate work.  The work is done by system becaus


Q. Supply Fan - air-conditioning guidelines? Recheck final air quantities and static pressure. Indicate location of motor and belt guard. For fans located in plenums ensure ade


Explain the study of readial Drilling machine with spindle The objective of this study is to study of readial Drilling machine with spindle. As in Radial Drilling machine th

A rigid bar ABCD is hinged at A and supported by a bronze rod, 2m long, and a steel rod 1m long as shown in figure A load of 80 KN is applied at end B. Determine the stresses in ea

Let consider the breakwater configuration shown in the figure below. The incident wave conditions at the breakwater are a wave height of 1.5m, wave period of 7.0s and a wave crest

crowning of pulley