EXCERISE
Short-Answer Questions
1. Define volume. Write its SI unit.
Answer- Volume of an object is the space occupied by it. It's S.I unit is m³.
Answer- The density of a material is defined as its mass per unit volume. The S.I unit of Density is kg/ m³.
Answer- The relative density of a substance is defined as the ratio of the density of a substance to that of water. It's has no unit.
Answer- The weight of a body is the force with which it is attracted by gravity. S.I unit of Weight is newton (N).
Answer- Weight = constant x mass
Answer- Relative density of water is 1.
Long-Answer Questions:
1. Draw an irregular shape on a graph paper and explain how you would calculate its area.
Answer- Irregular shape is placed on the graph paper and outline is drawn.
Calculate-
The number of complete squares within the outline = 17
The number of squares with half or more within the outline = 14
The total number of squares = 31
The area of each square = 1 cm³
The area of the irregular shape = 31 cm³
Answer- We need a measuring cylinder, a small stone which can move easily inside the cylinder, some string and water. Take some water in the cylinder, as in Figure . Read the level of water on the scale marked on the wall of the cylinder. Then tie the string around the stone, and lower it gently into the water till it is completely submerged, as in Figure . Read the level of water again. The difference between the two readings gives the volume of the stone. For the Case shown in Figure
The initial reading = 20 ml
The final reading = 24 ml
The volumeof the stone= 24 ml- 20 ml
= 4 ml = 4 cm³
Answer- To determine the density of a cube , we need to find out mass of the cube using physical balance and volume by using formula.
Density of a cubex= Mass of a cube ÷ Volume of a cube.
Answer- The density of a material is defined as its mass per unit volume. The S.I unit of Density is kg/ m³
Objective Questions
Choose the correct option.
1. Which of the following is not a unit of volume?
(a) cc
(b) mL
(c) m²
(d) L
(a) 9.8 N.
(b) 1 N
(c) 98 N
(d) 0.98 N
(a) Kerosene (800 kg/m³)
(b) Ice (916 kg/m³)
(c) Cork (200 kg/m³)
(d) Mercury (13600 kg/m³)
(a) Mass
(b) Weight
(c) Volume
(d) Area
Fill in the blanks.
1. The capacity of a container is the volume of the liquid it can hold.
2. The unit of capacity is the same as volume
3. A substance of relative density greater than 1 is heavier than water.
4. The mass of a body is the amount of matter in the body.
5. The greater the mass of a body, the more is its weight.
Write True or False.
1. The area of a piece of cardboard of irregular shape can be found by using a string and a scale. False
2. The relative density of a substance has the same numerical value as its density in SI units. False
3. A substance with a relative density of less than 1 is lighter than water. True
4. The greater the mass of a body, the greater is its volume. False
5. The density of water is 1000 kg/m³. True
6. Ice is lighter than water. True
7. Weight is a force. True
Numericals:
1. Find the mass of an ice cube of edge 2 cm. The density of ice is 9000 kg/m³.
Answer-
Density = 9000 kg/ m³ = 9 g/ cm³
Volume = 2x2x2 = 8 cm³
Density = Mass ÷ Volume
Mass = Density x Volume
= 9 g/ cm³ x 8 cm³ = 72 g
Answer-
Density = 800 kg / m³ = 0.8 g/ cm³
Mass of kerosene = 200 g - 120 g = 80 g
Volume = Mass ÷ Density
= 80 g ÷ 0.8 g/ cm³ = 100 cm³
Answer-
Given Mass = 1.8 kg = 1800 g
Volume = 250 cm³
Density = Mass ÷ Volume
= 1800 g ÷ 250 cm³
. = 7. 2 g / cm³ = 7200 kg / m³
Answers:
Volume of metal = 21 ml = 21 cm³
Mass = 56.7 g
Density = Mass ÷ Volume
. = 56.7 g ÷ 21 cm³
= 2.7 g/ cm³
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