Class VII Physics Unit 1 Quiz

Physical Quantities and Measurements

• Space occupied by an object is referred to as Volume.
• Speed can be calculated by Distance / Time; example, traveling 150m in 1min results in a speed of 2.5 m/s.
• Area of a rectangle is calculated using Length x Width; for a paper of 1.5 m x 20 cm, the area equals 300 cm² or 0.3 m².
• Density measures mass per unit volume; density of alcohol 0.8 g/cm³ translates to 800 kg/m³ in SI units.
• In astronomy, distances between stars are measured in Parsecs, Astronomical Units, or Light years.
• Fundamental quantities in mechanics are Length, Mass, and Time.
• Derived units include measurements such as Metre³ and not basic units like Metre or Kelvin.
• Litre is not considered an SI unit, while Metre, Second, and Kilogram are SI units.
• To find the mass of a wooden block with a density of 0.8 g/cm³ and volume 60 cm³: Mass = Density x Volume = 48 g.
• MKS system represents units of Metre, Kilogram, and Second.

Unit Review

• Formula for Volume of a cube is s³, where 's' is the side length.
• Density (D) is calculated by the formula D = Mass/Volume.
• Density and volume computations can be practiced using object measurements.
• To measure the volume of an irregular object, water displacement method is used: difference in water levels before and after submerging gives the volume.
• Density is defined as mass per unit volume; SI unit is kg/m³.
• Volume of liquid in the container given dimensions can be calculated as Length x Width x Height.
• Converting g/cm³ to kg/m³ involves multiplying by 1000 for correct SI unit representation.
• Weight on different planets varies depending on gravitational pull; Weight = Mass x g.

Key Concepts

• Mass refers to the quantity of matter, while weight is the force of gravity acting on that mass.
• To convert 0.25 m to cm, multiply by 100; to convert 25 cm to km, divide by 100,000.
• Area of a square is calculated from the side length; for an area of 64 cm², the side is 8 cm.
• Area of circle is found using the formula πr²; for radius 7 m, area is approximately 154 m².
• To measure the volume of a cube, use s³; for side 6 cm, volume calculates to 216 cm³.
• Volume of a sphere can be calculated using the formula (4/3)πr³; for radius 5 cm, volume is 523.33 cm³.

Real-Life Applications

• Density plays a key role in objects floating or sinking; lower density substances float.
• Examples include swimming, buoyancy in boats, and hot air balloons, which depend on density differences.
• Hydrogen bubbles float due to lower density compared to soap water.
• Weight differences across planets can be explained by variations in gravitational acceleration.

Additional Points

• Objects with densities lower than that of a liquid will float, while those with higher densities will sink.
• Knowledge of densities helps predict behavior of materials in different environments, emphasizing the importance of understanding physical properties in science.

Test your knowledge on physical quantities and measurements in this quiz designed for Class VII students. Questions cover concepts such as volume, speed, and basic definitions in physics. Enhance your understanding of these fundamental topics before your next exam!