# measurement chapter in physics for class 9

Then, we know that the time period is directly proportional to the square root of the length of the pendulum.

= 1.496 × 1011 m, Centimeter (cm) and millimeter (mm) are units of length smaller than a metre.

= Pitch/No. Therefore, the value of 1 m.s.d. Hence, a vernier callipers can measure length correct up to 0.01 cm. A pendulum with the time period of oscillation equal to two seconds is known as a seconds pendulum.

Fundamental unit: The units of the fundamental quantities are called fundamental unit. Therefore, vernier scale reading = 6 × 0.01 cm = 0.06 cm Total reading = m.s.r. = 5/10 = 0.5 s, Value of 1 m.s.d. of vernier callipers = 0.01 cm Main scale reading = 1.8 cm Since 4th division of the main scale coincides with the main scale, i.e. = Pitch/No. From this graph, the value of acceleration due to gravity (g) can be calculated as follows. Selina Publishers Concise Physics for Class 9 ICSE Solutions all questions are solved and explained by expert teachers as per ICSE board guidelines. Negative zero error: On bringing the two jaws together, if the zero mark of the vernier scale is on the left of the zero mark of the main scale, then the error is said to be negative. (a) Vernier callipers (b) Metre scale (c) Screw gauge. Positive zero error: On bringing the two jaws together, if the zero mark of the vernier scale is on the right of the zero mark of the main scale, the error is said to be positive. All Do You Known ?

= Value of 1 m.s.d./number of divisions on vernier scale = 1 mm/10 = 0.1 mm or 0.01 cm, There are 20 divisions in 1 cm on the main scale. Astronomical unit (A.U.) = 1 mm /10 = 0.1 mm = 0.01 cm. We cannot have a heavy mass having the size of a point and string having no mass. Measurement of diameter of wire with a screw gauge: The wire whose thickness is to be determined is placed between the anvil and spindle end, the thimble is rotated until the wire is firmly held between the anvil and spindle. unit of time is second (s). The least count of a metre rule is 1 cm. 1 min = 60 s 1 yr = 3.1536 × 107 s. A leap year is the year in which the month of February has 29 days. (p) = 47 Circular scale reading = p × L.C. L.C. = 4 Zero error = + (4 × L.C.)

= +6 × 0.01 cm = +0.06 cm.

of divisions on the circular scale = 50 (i) Pitch = Distance moved ahead in one revolution = 1 mm/1 = 1 mm. Pendulum A will take more time (twice) in a given time because the time period of oscillation is directly proportional to the square root of the length of the pendulum. For example, for the scales shown, the least count is 0.01 cm and the 6th division of the vernier scale coincides with a main scale division. It is measured in second (s). = 0.5 / 0.001 = 500.

of divisions on the circular head = (1/100) mm = 0.01 mm or 0.001 cm, (ii) Main scale reading = 2mm = 0.2 cm No.

of a screw gauge is the distance moved by it in rotating the circular scale by one division. The units of the fundamental quantities are called fundamental unit. This gives a to and fro motion about the mean position to the pendulum. = 1 mm / 100 = 0.01 mm = 0.001 cm.

A unit is defined as a convention to define an amount of physical property in a specific system of units.. Then, the value of T2 is to be noted at a and b, the value of l at c and d. Then, where g is the acceleration due to gravity at that place. Therefore, the vernier scale reading = 4 × 0.01 cm = 0.04 cm Total reading = Main scale reading + vernier scale reading = (1.8 + 0.04) cm = 1.84 cm, (b) Observed reading = 1.84 cm Zero error = -0.02 cm Correct reading = Observed reading – Zero error (with sign) = [1.84 – (-0.02)] cm = 1.86 cm, L.C. The slope of the straight line can be found by taking two points P and Q on the straight line and drawing normals from these points on the X- and Y-axis, respectively. Zero error = – (10 – 6) × L.C. The S.I.

If a screw moves by 1 mm in one rotation and it has 100 divisions on its circular scale, then pitch of screw = 1 mm. To measure the time period of a simple pendulum, the bob is slightly displaced from its mean position and is then released. 1 km = 1000 m 1 A.U. 1. of divisions = 100 Length of each division = Total length/total no.

Get Measurements and Experimentation, Physics Chapter Notes, Questions & Answers, Video Lessons, Practice Test and more for CBSE Class 10 at TopperLearning. The thickness of the wire could be determined from the reading as shown in the figure below. + circular scale reading = (4 + 0.94) mm = 4.94 mm, Pitch of the screw gauge = 0.5 mm L.C. = Pitch of the screw gauge/total no. Therefore, total reading = main scale reading + vernier scale reading = 1.2 cm + (p × L.C. L.C. of divisions on its circular scale. of a screw gauge: The L.C. Therefore, circular scale reading = 46 × 0.01 = 0.46 mm Total reading = Main scale reading + circular scale reading = (2.5 + 0.46) mm = 2.96 mm, (a) Screw gauge (b) Screw gauge (c) Vernier calipers (d) Screw gauge. The zero error is of two kinds. The pitch of the screw = 1 mm L.C. A second is defined as 1/86400th part of a mean solar day, i.e.

= 3.3 + 0.06 = 3.36 cm, Pitch of a screw gauge = 0.5 mm No. The main scale is graduated to read up to 1 mm and on vernier scale, the length of 10 divisions is equal to the length of 9 divisions on the main scale. Unit is a quantity of constant magnitude which is used to measure the magnitudes of other quantities of the same manner.

(a) The time period of oscillations is directly proportional to the square root of the length of the pendulum. = Pitch/No. of the screw gauge = 0.001 mm No. (ii) L.C. The statement ‘the distance of a star from the Earth is 8.33 light minutes’ means that the light from the star takes 8.33 minutes to reach Earth.

(d) The time period of oscillations of simple pendulum is inversely proportional to the square root of acceleration due to gravity. Then, Value of n divisions on vernier = (n – 1) x. Vernier constant is equal to the difference between the values of one main scale division and one vernier scale division. (iv)Time period: This is the time taken to complete one oscillation. = 45 x 0.001 cm = 0.045 cm Total reading = M.s.r. For example, for the scales shown, the least count is 0.01 cm and the sixth division of the vernier scale coincides with a certain division of the main scale. You can download the Selina Concise Physics ICSE Solutions for Class 9 with Free PDF download option. The number of this vernier division is subtracted from the total number of divisions on the vernier scale and then the difference is multiplied by the least count. The least count of a screw gauge can be increased by decreasing the pitch and increasing the total number of divisions on the circular scale. of division of circular head in line with the base line (p) = 27 Circular scale reading = (p) × L.C. A simple pendulum is a heavy point mass (known as bob) suspended from a rigid support by a massless and inextensible string. of divisions on the circular scale = 100, (i) L.C.

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