Physics assignment Vishakha 3614 Submitted by, Aarti 1179 Manpreet 3638 Renu 3801 Manpreet kaur 3660

Submitted to J.P. Sir and Mahender sir By the students of class b.sc. 2nd computer science

Topic: To find height of an inaccessible object using a sextant

SEXTANT Sextant is based on the principle that a reflected ray is turned through double the angle through which the mirror is rotated. It is used to find the height of buildings, mountains and altitude the sun .

APPRATUS A sextant , 50 m measuring tape, plumb line, spirit level, sextant stand with rigid clamp, a piece of chalk or marked arrow heads on board.

B A x C y D 02

Theory When the foot of the object cannot be reached directly and distance batween the foot and the sextant cannot be measured is said to be inaccessible. To find the height AB=h of such an object the angles 01 and 02 which it subtends at two diff. positions C and D distance x apart are found out by clamping the sextant at these points.

Now d=x+y = hcot02 And y= hcot01 So, hcot02-y = hcot02- hcot01 =h(cot02-cot01) Hence h= x\cot02-cot01 Now x can be measured with the help of measuring tape, therefore h can be calculated.

Procedure 1. Mark an arrow head as reference point at the distant object for which the height is to be determined. Adjust the height of the axis of the telescope of sextant is clamped in a vertical position the direct point of this reference mark is seen through the telescope. The height of the top of the object is to be determined w.r.t . This mark. Make the scale vertical with plump line. 2. Move the index arm till the direct and reflected images of the reference arrow overlapeach other and are equally bright. For the correctly adjusted sextant this will happen when the zero f vernier coincides with nearly the zeroes of the main scale.

3. Now move the index arm so that half of the field of views moves past the stationary images of the fixed reference mark.Go on moving till the reflected image of upper point i.e. top of the object coincides with the direct image of the arrow. 4. Move the sextant either forward or backward through a known distance ‘x’ i.e. the centre of these two points are in the same straight line .

5. Repeat the experiment for a third point E .

OBSERVATIONS NO. Position of sextant Sextant scale reading Diff. b-a=0 cot0 h Initial reading=a Final reading=b 1. C=1450 2.5.,5’, 36” 10.,23’,24” 01= 7.5.,18’,48” 7.3 1.25 2. D=1570 2.5., 16’,12” 11.,30’36” 02= 8.5.,14’,24” 6.5 1.57 3. E=1660 3.5.,47’, 48” 11.5.,37’,24” 03= 8.5.,10’,24” 6.43 1.37

CALCULATIONS 1. From 1. and 2. CD= x1= 1.00m h1=x1/cot02-cot01= 1.00/0.80= 1.25m 2. from 2. and 3. DE= x2= 0.60m h2= 0.60/0.07=1.57m 3. from 3. and 1. CE=1.20m h3=1.20/0.87=1.37m

Mean Height = h1+h2+h3/3 = 1.25+1.57+1.37/3=3.77m

Result Height of inaccessible object=3.77m Actual height of object=3.60m percentage error=4.7%

THANKYOU