The mass of a box measured by a grocer’s balance is 2.30 kg. Two gold pieces of
masses 20.15 g and 20.17 g are added to the box. What is (a) the total mass of the
box, (b) the difference in the masses of the pieces to correct significant figures ?
The length, breadth and thickness of a rectangular sheet of metal are 4.234 m, 1.005 m, and
2.01 cm respectively. Give the area and volume of the sheet to correct significant figures.
State the number of significant figures in the following :
(a) 0.007 m2
(b) 2.64 × 1024 kg
(c) 0.2370 g cm–3
(d) 6.320 J
(e) 6.032 N m–2
(f) 0.0006032 m2
The photograph of a house occupies an area of 1.75 cm2
on a 35 mm slide. The slide
is projected on to a screen, and the area of the house on the screen is 1.55 m2
. What
is the linear magnification of the projector-screen arrangement.
A student measures the thickness of a human hair by looking at it through a
microscope of magnification 100. He makes 20 observations and finds that the average
width of the hair in the field of view of the microscope is 3.5 mm. What is the
estimate on the thickness of hair ?
Which of the following is the most precise device for measuring length :
(a) a vernier callipers with 20 divisions on the sliding scale
(b) a screw gauge of pitch 1 mm and 100 divisions on the circular scale
(c) an optical instrument that can measure length to within a wavelength of light ?
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