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$3. An object of mass 100 \mathrm{~g} is immersed in water as shown in the figure 1.27 what is the density of the material from which object is made?a) 0.4 \mathrm{gcm}^{3} b) 0.9 \mathrm{gcm}^{3} c) 1.1 \mathrm{gcm}^{3} d) 2.5 \mathrm{gcm}^{3} Fig 1.27$

$1.6 What role SI units have played in the development of science?$

$iii. Amount of a substance in terms of numbers is measured in:(a) gram(b) kilogramme(c) newton(d) mole$

$5. A chips wrapper is 4.5 \mathrm{~cm} long and 5.9 \mathrm{~cm} wide. Its area upto significant figures will bea) 30 \mathrm{~cm}^{2} b) 28 \mathrm{~cm}^{2} c) 26.55 \mathrm{~cm}^{2} d) 32 \mathrm{~cm}^{2}$

$1.6 On closing the jaws of a Vernier Callipers zero of the vernier scale is on the right to its main scale such that 4th division of its vernier scale coincides with one of the main scale division. Find its zero error and zero correction.$

$ii. Which one of the following unit is not a derived unit?(a) pascal(b) kilogramme(c) newton (d) watt$

$1.11 Why do we need to measure extremely small interval of times?$