**DENSITY**

**1 A block of iron is much heavier than a block of wood of the same size. Which has the greater density, iron or wood?**

**2 lf a block of a material has a volume of 6 m**

^{3}and a mass of 48 kg, what is its density?**3 What is the volume of 72 g of copper? Density of copper = 9 g/cm**

^{3}.**4 What is the mass of 4 m**

^{3}of soil? Density of soil = 2 g/cm^{3}**5 Water has a density of 1 g/cm**

^{3}(1000 kg/m^{3}). Which of the following will float in water?**Ice (920 kg/m**

^{3}); wood (0.6 g/cm^{3}); carbon (2300 kg/m^{3}).**6 (a) What two forces act on an object immersed in a liquid?**

**(b) If the object sinks which is the bigger of these two forces?**

**7 When an object floats in a liquid, what is the upthrust on it equal to?**

**8 What is the upthrust in newtons on a 50 kg lump of wood floating in water? (g = 10 N/kg)**

**9 A 1000 kg boat floats in water. What is the weight of water displaced by the boat?**

**10 A block has a mass of 5 kg in air and an apparent mass of 4.5 kg in water.**

**(a) What is the loss in weight of the block?**

**(b) What is the weight of water displaced?**

**(c) What is the volume of the block?**

**(d) What is the density of the block?**

**11 The same block is now immersed in brine of density 1100 kg/m**

^{3}.**(a) What is the upthrust on it?**

**(b) What is its weight in brine?**

**12 A balloon filled with hydrogen will float in air but when it is burst the rubber of the balloon will fall to the ground. Why?**

**13 If a lump of plasticine is stuck to the hydrometer in diagram A, what will happen to the hydrometer?**

**14 Why should you put your head as far back in the water as you can if you are trying to float?**

**15 A lump of iron will sink in water but if you make it into a hollow watertight ball it will float. Why?**