If mass of an object be 3 kg , then its weight on earth is = 3 × 9 . 8 N . Can you say what will be its weight on the moon?

Given that, Mass of the object is m = 3 kg Acceleration due to gravity on the earth is g = 9 . 8 m s - 2 Weight on earth W e = 3 × 9 . 8 = 29 . 4 N We know that, Weight W = m g Acceleration due to gravity on moon is g m = g 6 Therefore, Weight on the moon W m = 3 × 9 . 8 6 = 4 . 9 N

Fill up the table below: Incidents that happen in the atom Number of electrons increases/decreases/remain unchanged Total number of protons compared to electrons increases/decreases/unchanged Total negative charge of electrons relative to the total positive charge of protons increases/decreases. Net charge of the atom positive/negative Chargeless atom gets an electron Chargeless atom gives up electron

An atom that gains or loses an electron becomes an ion. If it gains an electron, it becomes a negative ion, so the atom ion is an anion. If it loses an electron, it becomes a positive ion, so the atom ion is a cation. Incidents that happen in the atom Number of electrons increases/decreases/remain unchanged Total number of protons compared to electrons increases/decreases/unchanged Total negative charge of electrons relative to the total positive charge of protons increases/decreases. Net charge of the atom positive/negative Chargeless atom gets an electron increases decreases increases Negatively charged Chargeless atom gives up electron decreases increases decreases Positively charged

The mathematical expression for the amount of heat gained or given up by a body is Q = m × s × ( t 2 - t 1 ) . Here instead of ' t ' ( t 2 - t 1 ) is written, where t 1 , is the initial temperature and t 2 , is the final temperature. Using this mathematical expression fill-up the blanks below. Name of the substance Mass (m) g Specific heat (s) calorie/g C Increase or decrease in temperature ( t 2 - t 1 ) C Heat absorbed of given up (calorie) Q = m × s × ( t 2 - t 1 ) . . Aluminium 400 0 . 21 70 - 30 Copper 100 0 . 09 90 - 50 Lead 600 0 . 03 80 - 25 Silver 80 0 . 05 35 - 25

The amount of heat gained or absorbed by a body to raise its temperature depends on three factors. These are the increase in temperature of the body, mass of the body and the material of the body. Name of the substance Mass (m) g Specific heat (s) calorie/g C Increase or decrease in temperature ( t 2 - t 1 ) C Heat absorbed of given up (calorie) Q = m × s × ( t 2 - t 1 ) . Aluminium 400 0 . 21 70 - 30 Q1= 400 × 0 . 21 × 40 = 3360 Copper 100 0 . 09 90 - 50 Q2= 100 × 0 . 09 × 40 = 360 Lead 600 0 . 03 80 - 25 Q3= 600 × 0 . 03 × 55 = 990 Silver 80 0 . 05 35 - 25 Q4= 80 × 0 . 05 × 10 = 40

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Why does rain fall on the earth from the sky?

Important Questions on Physical Environment

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8th West Bengal Board

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 8>Q 2

Why does a shedded tree leaf fall on the ground?

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8th West Bengal Board

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 8>Q 3

Why does the earth revolve around the sun?

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 8>Q 4

Why does not the moon fall towards the earth like a shedded leaf of a tree?

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8th West Bengal Board

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 9>Q 1

If mass of an object be

3 kg

, then its weight on earth is

= 3 \times 9.8 N

. Can you say what will be its weight on the moon?

MEDIUM

8th West Bengal Board

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 10>Q 1

Fill up the table below:

Incidents that happen in the atom	Number of electrons increases/decreases/remain unchanged	Total number of protons compared to electrons increases/decreases/unchanged	Total negative charge of electrons relative to the total positive charge of protons increases/decreases.	Net charge of the atom positive/negative
Chargeless atom gets an electron
Chargeless atom gives up electron

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8th West Bengal Board

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 11>Q 1

The mathematical expression for the amount of heat gained or given up by a body is

Q = m \times s \times (t_{2} - t_{1}) .

Here instead of

' t' (t_{2} - t_{1})

is written, where

t_{1}

, is the initial temperature and

t_{2}

, is the final temperature. Using this mathematical expression fill-up the blanks below.

Name of the substance	Mass (m) g	Specific heat (s) calorie/g C	Increase or decrease in temperature $(t_{2} - t_{1})$ C	Heat absorbed of given up (calorie) $Q = m \times s \times (t_{2} - t_{1}) .$ .
Aluminium	$400$	$0.21$	$70 - 30$
Copper	$100$	$0.09$	$90 - 50$
Lead	$600$	$0.03$	$80 - 25$
Silver	$80$	$0.05$	$35 - 25$

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8th West Bengal Board

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 12>Q 1

Question Image

As in the figure, the piece of solid wax sinks in the molten wax. In contact with hot molten wax, the solid wax melts very fast. The density of solid wax is higher than the density of liquid wax.

Answer the following questions:
Whether the volume increases or decreases when liquid wax became solid wax?

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Environment and Science Class 8>Chapter 1 - Physical Environment>Exercise 12>Q 2

Question Image
In the figure, the piece of ice floats on water. The density of the solid ice is less than the density of water.

Answer the following question:
Whether the volume of water increases or decreases when it freezes to ice?

Why does rain fall on the earth from the sky?

Important Questions on Physical Environment

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