G. Long-answer questions
1. How is time related to motion? Take the
help of an example to answer.
2. What are different types of motion? Explain
two with the help of examples.
3. Why do we need to measure things?
4. How will you find out the circumference of
a ten rupee coin?
5. Wheel of a bicycle has more than one type
of motion. Explain.
Answers
Answer: Question 1:
Which of the following are physical quantities? Speed of a car, how angry a person is, distance from earth to sun, how much a mother loves her child.
ANSWER:
Speed of a car and the distance from earth to sun are the only physical quantities, as they both can be measured and expressed in terms of fundamental quantities. But, how angry a person is or how much a mother loves her child are the emotions and can not be measured or expressed in terms of fundamental quantities. So, they are not physical quantities.
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Question 2:
Does a standard unit remain the same on the moon as it is on the earth?
ANSWER:
A standard unit is a fundamental measure of a physical quantity. It does not matter where we are, the physical quantities will always be expressed in a similar way. The standard unit for length is 'meter', for mass, it is 'kilogram' and for the time it is 'second'. These units are fundamentals, which will remain the same on the moon as well. For example, Gravity on the moon is different than the gravity on the earth, but the standard unit to measure the gravity on earth and the moon are the same, i.e. m/s2.
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Question 3:
Choose the correct SI unit.
Length: metre, centimetre or foot;
Mass: kilogram or gram
Time: hour or second
ANSWER:
SI units are the fundamental units for various physical quantities accepted all over the world. The Si unit given for length is 'meter', for mass it is 'kilogram' and for the time it is 'second'. Though length, mass and time can be expressed in terms of other units as well but these are the standard units used uniformly all over the world.
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Question 4:
Which of these is the correct way of writing
a. 10 kg or 10 kgs _________
b. 5 cm or 5 cms _________
c. 1 kg. or 1 kg _________
d. 20 cm. or 20 cm________
ANSWER:
Units are always expressed as singular words and their short abbreviation is taken as the full expression. The correct way of writing the given quantities is as follows:
(a) 10 kg
(b) 5 cm
(c) 1 kg
(d) 20 cm
.