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UNIVERSAL EDUCATION CISCE 2023-24 CLASS VII PHYSICS Unit 1 - Physical Quantities and Measurements Select the correct alternative: 1. T...

UNIVERSAL EDUCATION CISCE 2023-24 CLASS VII PHYSICS Unit 1 - Physical Quantities and Measurements Select the correct alternative: 1. The space occupied by object is called: a. Area b. Volume c. Density d. Acceleration 2. A boy travels a distance 150m in 1 min. His speed is: a. 150 m/s b. 25 m/s c. 2.5 m/s d. 9 m/s 3. A piece of paper of dimensions 1.5 m x 20 cm has area: a. 30 m2 b. 300 cm2 c. 0.3 m2 d. 3000 m3 4. The density of alcohol is 0.8 g cm-3. In S.I. unit, it will be: a. 0.8 kg m-3 b. 0.0008 kg m-3 c. 800 kg m-3 d. 8 x 103 kg m-3 5. The unit used in astronomy to measure great distances between stars: a. Parsec b. Angstrom c. Astronomical Unit d. Light year 6. In mechanic, the fundamental quantities are: a. Length, mass, velocity b. Mass, time, density c. Mass, time, pressure d. Length, mass, time 7. Which of the following is a derived unit: a. Metre b. Kelvin c. Metre3 d. Mole 8. Which of the following is not a SI unit? a. Metre b. Litre c. Second d. Kilogram 9. A block of wood of density 0.8 g cm has a volume of 60 cm3. The mass of block will -3 be: a. 60.8 g b.75 g c. 48 g d. 0.013 g 10. MKS system of units stands for: a. metre, kilogram, second b. milli, kilogram, sec c. metre, kilometre, second d. micro, kilolitre, scoville Unit Review ( Pg 16) 1. Fill in the Blanks i. Volume of a cube ii. Mass = density x volume iii. 1 = 1000 iv. 1 =  2. Select the correct option i. The density of aluminium is 2.7 g/ and brass is 4.8 g/. For the same mass, the volume of Ans c. Alluminium will be more than that of brass ii. One ml is equal to Ans. a.1 iii. Select the correct relation between mass, volume, density Ans. Ans. d. D = 3. A platinum bar measures 4.0 cm long,3.0 cm wide and 1.5 cm thick. It has a mass of 700.0 grams i. Calculate the volume of the platinum bar ii. Calculate the density of the platinum bar Ans. Given: length of platinum bar = 4.0cm Breadth of platinum bar = 3.0 cm Height of platinum bar = 1.5 cm Mass of platinum bar = 700.0 grams To find: Volume of platinum bar Density of platinum bar Solution : Volume of platinum bar = l x b x h = 4 x 3 1.5 = 18 Density of platinum bar = = = 38.89 g/ Q4 How will you measure the volume of an irregular object ? Include diagram. Sol. To measure the volume of a piece of stone Take a piece of brass, a measuring cylinder, fine thread of sufficient length and some water. Place a measuring cylinder on a flat horizontal surface and fill it partially with water. Note the reading of the water level very carefully. Now tie the piece of brass with a thread and dip it completely into water. We see that the level of water rises. Note the reading of the water level.  The difference in the two levels of water gives the volume of the piece of brass Initial level of water = 60 ml Level of water when brass is immersed = 80 ml Volume of water displaced = 80 ml 60 ml = 20 ml Volume of the piece of brass = 20cm3 Note: 1 ml = 1cm3 Q. 5 Define the term density and state its SI unit Ans. Density of a substance is defined as mass per unit volume of the substance. If M is mass of a substance and V is volume of the substance. Density = M/V SI unit of density = kg/ Q. 6 Determine volume of a liquid present in a container of dimensions 10 cm x 20 cm x 6 cm Ans. Volume of liquid in a container = lx b x h = 10 x 20 x 6 = 1200 Q. 7 The density of copper is 8.9 g/. What will be its density in kg/ Ans. Density of copper d = 8.9 g/ = 8.9 x 1000 kg/ [:. 1 g cm-3 = 1000 kg/ ] = 8900 kg m-3 Q.8 If the gravity of Jupiter is 2.5 times greater than Earth, then what will be the weight of 80 kg man on Jupiter?(g=9.8m/ ) Ans. Weight is not measured in Kg. It is measured in Newtons. If a person has a mass of 80kg, then they will weigh 80kg x9.8m/ or 784 Newtons on the Earth. That same person floating on the cloud tops of Jupiter would weigh 80Kg x 9.8m/s^2 x 2.5 or 1960 Newtons. 200Kg will be mass. Q.9 Difference between mass and weight Ans It refers to the measure of It is the measure of the the amount of force that Definition amount of matter present a acts on mass because of the body. pull of gravity.  Mass is the measure of Weigh is the measure of Meaning inertia. force. It stays the same everywhere, Weight will vary depending Location irrespective of location. on the location. The SI unit of mass is the SI Unit kilogram (kg). (N). Q. 10 Convert 0.25 m to cm and 25 cm to km Ans. 0.25 m to cm 1 m = 100 cm 0.25m x100 = 25 cm 25cm to km 1km = 1,00,000cm 25 cm /1,00,000 = 0.00025km Q.11 Calculate the side of a square having area of 64 Ans. Area of square = 64= Side = 64 Side = 8cm Q.12 Find area of circle with radius 7m Ans. Area of circle = A= x7x7 A = 154 Q.13 How would you calculate the volume of a cube of side 6cm? Ans. Volume of a cube = V= 6 x 6 x 6 = 216 Q.14 Calculate the volume of sphere with radius 5cm Volume of sphere =V V= V= 523.33 Q.15 Liquid iron is less dense than solid iron of the same mass. Why is this so? Ans. In most solids, such as iron, the molecules arrange themselves in a rigid, ordered fashion that ends up being, on average, closer from each other than they are in the  liquid phase, and thus more dense. that one makes it closer and the other farther apart than liquid. Suggested change: Iron in the liquid state occupies a greater volume than the same mass of iron in the solid state. Iron atoms are further apart in liquid iron than solid iron. Hence liquid iron is less dense than solid iron of the same mass Q.16 The volume of an object is 8 and it mass is 84 kg. Calculate its density? Ans. Volume of an object= 8 Mass of an object = 84 kg Density = = =10.5 kg/ Q. 17 Objects with densities lower than that of a liquid, float on the liquid Objects with densities higher than that of a liquid, sink in the liquid. The table shows the densities of four different types of plastic. The plastics are al solids. Type of plastic Density d/cm3 1 polyethylene a. 0.91 2 polypropylene b. 0.94 3 cellulose acetate c1.28 4 polyvinyl chloride d. 1.38 The densities of two liquids are water 1.0 g/cm engine oil 0.92 g/cm Name a type of plastic from the table that will i. float in both engine oil and in water ii. sink in engine oil but float in water iii. sink in both engine oil and in water Ans. Float in both engine oil and in water polyethylene Sink in engine oil but float in water - polypropylene Sink in both engine oil and in water- cellulose, polyvinyl chloride Extra questions (HOTS)  1. Why do hydrogen bubbles float when hydrogen is passed through soap water? Ans. Since gas is lighter in density than soap water the bubbles float on it. 2. Why is the weight of the same object different on different planets? Ans. Weight of an object, W is given as W = mg Where, m = mass of the object and g = acceleration due to gravity of a place We know that acceleration due to gravity is different at different planets. Hence, the weight of same object differs on different planets. 3. Give some real-life examples where density matters? Ans. Swimming - We can swim because our density is just barely lower than the density of water. Party balloons are possible because we fill them with a low-density substance. Boating - Boats float because they are less dense than water. Air ships and hot air balloons fly because we design them to have the same density as air. Suggested change: The human can float in water because a human submerged in water weighs less than the water itself, because the lungs are full of air like a balloon, and like a balloon, the air in the lungs lifts you to the surface naturally. Test Yourself: 1. Choose the correct option: a. The SI unit of density is - Ans. kg/m3 b. The area of the square with the 25 cm is - Ans. 625cm2 c. The volume of a cylinder with a radius 7cm and height 4cm is- Ans. 616cm 2. State True or False. a. A cork floats on water because its density is greater than that of water. Ans. False b. Area is the amount of space occupied by an object. Ans. True c. It is easy to swim in river water than in sea water. Ans. False d. A piece of iron (density 7.6 g/cm3) floats in mercury (density 13.6 g/cm3) Ans. True