Let's solve each question one by one with explanations:
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1. Light year is the unit of?
Options:
a) Distance
b) Time
c) Density
d) Both length and time
Answer: a) Distance
Explanation:
A *light year* is the distance that light travels in one year in a vacuum. It is used to measure large distances in space (e.g., between stars).
Even though it includes "year," which is a unit of time, the term "light year" refers to
distance, not time.
✔ So, correct answer:
a) Distance
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2. SI unit of density is ________
Options:
a) Kg/m²
b) Kg/m³
c) Kg/m
d) g/m³
Answer: b) Kg/m³
Explanation:
Density = Mass / Volume
- SI unit of mass = kilogram (kg)
- SI unit of volume = cubic meter (m³)
So, SI unit of density =
kg/m³
Note: While gram per cubic centimeter (g/cm³) is commonly used, the
SI unit is
kg/m³.
✔ Correct answer:
b) Kg/m³
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3. Two spheres have equal mass and volume in the ratio 2:1. The ratio of their densities is ________
Given:
- Mass of both spheres is
equal → let’s say mass = M
- Volume ratio = 2:1 → Let V₁ = 2V, V₂ = V
We know:
Density = Mass / Volume
So:
- Density of first sphere = M / (2V)
- Density of second sphere = M / V
Now find the ratio:
(Density₁) : (Density₂) = (M/(2V)) : (M/V) = (1/2) : 1 =
1:2
✔ Correct answer:
a) 1:2
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4. Which of the following is a derived unit?
Options:
a) mass
b) time
c) area
d) length
Answer: c) area
Explanation:
-
Fundamental units are basic units like mass, length, time, etc.
-
Derived units are formed from fundamental units.
- Area = Length × Length → m² → derived from length
- Mass, time, and length are all
fundamental units.
✔ So,
area is a derived unit.
Correct answer:
c) area
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5. Which of the following is correct?
Options:
a) 1L = 1 cc
b) 1L = 10 cc
c) 1L = 100 cc
d) 1L = 1000 cc
Answer: d) 1L = 1000 cc
Explanation:
- 1 liter (L) = 1000 milliliters (mL)
- 1 mL = 1 cubic centimeter (cc)
So, 1 L = 1000 mL = 1000 cc
✔ Correct answer:
d) 1L = 1000 cc
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✔ Final Answers:
1.
a) Distance
2.
b) Kg/m³
3.
a) 1:2
4.
c) area
5.
d) 1L = 1000 cc
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Parent Tip: Review the logic above to help your child master the concept of measurement worksheet grade 7.
