## Mass, weight and density Questions

1.  A squared brass plate is 2mm thick and has a mass of 1.05kg. The density of brass is 8.4g/cm. Calculate the length of the plate in centimeters. (3mks)

2.  A sphere has a surface area 18cm2. find its density if the sphere has a mass of 100g.  (3mks)

3.  Nyahururu Municipal Council is to construct a floor of an open wholesale market whose area is  800m2. the floor is to be covered with a slab of uniform thickness of 200mm. in order to make  the slab, sand, cement and ballast are to be mixed such that their masses are in the ratio 3:2:3. The  mass of dry slab of volume 1m3 is 2000kg. Calculate

(a) (i) The volume of the slab (2mks)

(ii) The mass of the dry slab. (2mks)

(iii) The mass of cement to be used. (2mks)

(b) If one bag of the cement is 50kg, find the number of bags to be purchased. (1mk)

(c) If a lorry carries 10 tonnes of ballast, calculate the number of lorries of ballast to be  purchased. (3mks)

4.  A sphere has a surface area of 18.0cm2. Find its density if the sphere has a mass of 100 grammes.

(3 mks)

5.  A piece of metal has a volume of 20 cm3 and a mass of 300g. Calculate the density of the metal

in kg/m3.

6.  2.5 litres of water density 1g/cm3 is added to 8 litres of alcohol density 0.8g/cm3. Calculate the

density of the mixture

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## Mass, weight and density Answers

 2. 4 x 3.142 x r2 = 18 R ~ 1.197Vol. = 4/3 x 3.142 x 1.197= 7.185cm3Density = 100 7.185= 13.92g/cm3 M1  M1 A1 03 3. (a) (i) 800 x 0.2= 160m3(ii) 160 x 2000= 320,000kg(iii) Cement = 2/8 x 320,000= 80,000(b) Bags = 80,000 50= 1600(c) Ballast = 3/8 x 320,000= 120,000 tonnes= 120 lorries M1A1M1A1M1A1B1 B1M1A1B1 10 4. B1  B1    B1 03

5.  Density = 300 x 1,000,000

20 x 1000

=15,000 kg/m3

6.  D = M

V

Mas = D x V

= 1g x 2500cm3

cm3

= 2500g……………………………………(i)

Mass = 0.8 x 8000

= 6400g ……………………………….(ii)

total mass = (2500 + 6400)g

= 8900g

Density of mixture = 8900g/cm3

10500

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