NY Regents Exam   Teasers   IQ Tests   Chemistry   Biology   GK   C++   Recipes   Search <  a href="/cgi/members/home.cgi" class="toplink">Members   Sign off

Discussion topic: Contributed Answer/Explanation to Q. 37

Viewing messages

 Page 1 of 2  > From: ratchet Reply 1 of 22 Reply Subject: Contributed Answer/Explanation to Q. 37 ``` This happens because the frquency of the applied repeated periodic forced vibrations becomes equal to the natural frequency of the rare view mirror ```Posted at: Sun Dec 27 16:28:14 2009 (GMT) From: ratchet Reply 2 of 22 Reply Subject: Contributed Answer/Explanation to Q. 38 ``` The name of the phenomenon taking place is resonance ```Posted at: Sun Dec 27 16:29:21 2009 (GMT) From: ratchet Reply 3 of 22 Reply View replies (1) Subject: Contributed Answer/Explanation to Q. 39 ``` In order to stop the violent vibrations we ```Posted at: Sun Dec 27 16:30:39 2009 (GMT) From: ratchet Reply 4 of 22 Reply Subject: Contributed Answer/Explanation to Q. 39 ``` In order to stop the violent vibrations we can change the speed of the motor bike or by tightening the screw of the rare view mirror ```Posted at: Sun Dec 27 16:32:04 2009 (GMT) From: sourima Reply 5 of 22 Reply Subject: Contributed Answer/Explanation to Q. 1 ``` 1:1 momentum for 1st body=20*5=100kg m\s^2 momentum of 2nd body=5*20=100kgm\s^2 therefore,ratio=1:1 ```Posted at: Thu Jan 7 17:30:00 2010 (GMT) From: ishan20 Reply 6 of 22 Reply Subject: Contributed Answer/Explanation to Q. 8 ``` focal length ```Posted at: Mon Jan 18 02:31:48 2010 (GMT) From: abirghosh050793 Reply 7 of 22 Reply View replies (1) Subject: Contributed Answer/Explanation to Q. 1 ``` 1 : 1 mp = 20 kg vp  = 5 m/s mq = 5 m/s vq   = 20 kg Ratio of the momenta of P and Q = mpvp  :  mqvq  = 20 x 5 : 5 x 20 = 1 : 1 ```Posted at: Tue Feb 9 11:47:38 2010 (GMT) From: abirghosh050793 Reply 8 of 22 Reply Subject: Contributed Answer/Explanation to Q. 1 ``` 1 : 1 mp = 20 kg vp  = 5 m/s mq = 5 m/s vq   = 20 kg Ratio of the momenta of P and Q = mpvp  :  mqvq  = 20 x 5 : 5 x 20 = 1 : 1 ```Posted at: Tue Feb 9 11:48:50 2010 (GMT) From: abirghosh050793 Reply 9 of 22 Reply Subject: Contributed Answer/Explanation to Q. 2 ``` 500 J mp = 20 kg vp  = 5 m/s Kinetic Energy of P  = 1/2  mp (vp) 2 = 20 x 5 x 5 J = 500 J ```Posted at: Tue Feb 9 11:53:15 2010 (GMT) From: abirghosh050793 Reply 10 of 22 Reply View replies (1) Subject: Contributed Answer/Explanation to Q. 3 ``` Fire tongs is an example of third class lever. MA = Effort Arm   Load Arm ```Posted at: Tue Feb 9 11:56:46 2010 (GMT) From: abirghosh050793 Reply 11 of 22 Reply Subject: Contributed Answer/Explanation to Q. 3 ``` Fire tongs is an example of third class lever.

MA = Effort Arm / Load Arm

For a third class lever, effort is in between fulcrum and load, so,

```Posted at: Tue Feb 9 11:58:09 2010 (GMT) From: abirghosh050793 Reply 12 of 22 Reply Subject: Contributed Answer/Explanation to Q. 4 ``` In vacuum Spring balance measures weight, not mass. In air weight of a body will be less than in vacuum due to the buoyancy of air. ```Posted at: Tue Feb 9 11:59:26 2010 (GMT) From: abirghosh050793 Reply 13 of 22 Reply Subject: Contributed Answer/Explanation to Q. 6 ``` It is because the specific latent heat of vaporisation of water is much higher than its specific heat capacity. Specific heat capacity of water = 4.2 J/g/oC Specific latent heat of vaporisation = 2268 J/g Heat needed to bring 'm' g of water to its boiling point from room temperature (25oC) = m x 4.2 x (100 - 25) J = 315 m J Heat needed to boil off 'm' g of water = m x 2268 J = 2268 m J Let the power be P. Time taken to bring 'm' g of water to its boiling point from room temperature (25oC)  = 315 m / P Time taken to boil off 'm' g of water = 2268 m / P Obviously, 2268 m / P is greater than 315 m / P. ```Posted at: Tue Feb 9 12:08:29 2010 (GMT) From: abirghosh050793 Reply 14 of 22 Reply Subject: Contributed Answer/Explanation to Q. 8 ``` Focal Length Only rays starting from the focus, after refraction emerges parallel to the principal axis and fall normally on the plane mirror to get reflected back in the same path. Thus the image is formed also on the focus. So, S is the focus, and OS is the focal length ```Posted at: Tue Feb 9 12:11:16 2010 (GMT) From: abirghosh050793 Reply 15 of 22 Reply Subject: Contributed Answer/Explanation to Q. 9 ``` on S Here the phenonmenon of the return of the rays to their starting point is independent of the distance between the lens and plane mirror. ```Posted at: Tue Feb 9 12:12:47 2010 (GMT) From: abirghosh050793 Reply 16 of 22 Reply Subject: Contributed Answer/Explanation to Q. 10 ``` A piece of red-cloth appears red in white light because it absorbs blue and green, and reflects only red. White light mainly contains red green and blue colours. Anything which absorbs blue and green, and reflects only red, will appear red in white light as only red colour reaches our eyes. ```Posted at: Tue Feb 9 12:15:21 2010 (GMT) From: abirghosh050793 Reply 17 of 22 Reply Subject: Contributed Answer/Explanation to Q. 12 ``` The far point of a normal person lie on the retina of his eyes, but for a myopic person it lies in front of the retina For a normal person the rays of light from a distant is focussed on the retina, facilitating clear vision, but for a myopic person, the rays are focussed in front of the retina, thus making distant vision blurred. ```Posted at: Tue Feb 9 12:17:53 2010 (GMT) From: abirghosh050793 Reply 18 of 22 Reply Subject: Contributed Answer/Explanation to Q. 14 ``` No Quality does not depend on the pitch, but on the waveform. If two different persons play even on identical guitars, the number of ubsidiary notes produced by them and their relative amplitudes with the principal note will not exactly match. So, the quality of their sounds will differ, even if they play notes of the same pitch. ```Posted at: Tue Feb 9 12:21:17 2010 (GMT) From: shafeek47 Reply 19 of 22 Reply Subject: Contributed Answer/Explanation to Q. 1 ``` 1:1 ```Posted at: Mon May 10 16:41:34 2010 (GMT) From: utsav13 Reply 20 of 22 Reply Subject: Contributed Answer/Explanation to Q. 2 ``` 250 Joules 1/2 x 20 x 5 x 5 = 250 joules```Posted at: Fri Feb 25 13:31:38 2011 (GMT) Page 1 of 2  >