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Fill in the blanksThe volume of a cube of side 1 cm is equal to..........................m3.The surface area of a solid cylinder of radius 2.0 cm and height 10.0 cm is equal to ........................ (mm)2.A vehicle moving with a speed of 18 km h–1covers..................................m in 1 s.The relative density of lead is 11.3. Its density is ....................................g cm–3 or . ...kg m–3. |
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Answer» 1 cm = (1/100)m Volume of the cube = 1 cm3 But, 1 cm3 = 1 cm × 1 cm × 1 cm = (1/100) m x(1/100) m x(1/100) m 1 cm3 = 10-6m3 Hence, the volume of a cube of side 1 cm is equal to 10–6 m3. The total surface area of a cylinder of radius r and height h is S = 2πr (r + h). Given that, r = 2 cm = 2 × 1 cm = 2 × 10 mm = 20 mm h = 10 cm = 10 × 10 mm = 100 mm = 15072 = 1.5 × 104 mm2 S = 2 x 3.14 x 20 x (20 + 100) Using the conversion, 1 km/h = (5/18)m/s 18 km/h = 18 x (5/18) = 5 m/s Therefore, distance can be obtained using the relation: Distance = Speed × Time = 5 × 1 = 5 m Hence, the vehicle covers 5 m in 1 s. Relative density of a substance is given by the relation, Relative density = (Densityof substance/Density of water) Density of water = 1 g/cm3 Density of lead = Relative density of lead x Density water = 11.3 x 1 = 11.3 g/cm3 Again, 1g = (1/1000) kg 1 cm3 = 10–6 m3 1 g/cm3 = 10-3/10-6 kg/m3 = 103 kg/m3 11.3 g/cm3 = 11.3 × 103 kg/m3 |
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