4.22 light years.

m/s

a. Volume of a cube = side \(\times\) side \(\times\) side
= 3 cm \(\times\) 3 cm \(\times\) 3 cm = 27 cubic cm or \(\mathrm{cm}^{3}\)
b. Volume of a cylinder \(=\pi \times(\text { radius })^{2} \times \text { height }\)
\(=22 / 7 \times 3 \times 3 \times 7=198 \mathrm{~m}^{3} .\)

Density of gold is 19,300 kg/m³

Iron ball sinks in all the liquids apart from mercury.

Volume of a cylinder = π r² h

Area, Volume, Speed, Electric charge and Density.

One light year is defined as the distance travelled by light in vacuum during the period of one year.
1 Light year = 9.46 \(\times\) 10¹⁵m

Physical quantities which can be obtained by multiplying, dividing or by mathematically combining the fundamental quantities are known as derived quantities.
Ex: Area, volume

(i) Place the irregular object on a graph sheet and draw its outline. Then remove the object
(ii) To find the area enclosed by the outline count the number of small squares.
(iii) If more than half-a-square is inside the boundary, count it as one otherwise neglect it.
(iv) The area of each small square is 1sq. mm.
(v) Area of the irregular object = No. of squares x 1 sq.mm.

Take a leaf from any one of trees in your neighbourhood. Place the leaf on a graph sheet and draw the outline of the leaf with a pencil. Remove the leaf. You can see the outline of the leaf on the graph sheet.
i) Now count the number of whole squares enclosed within the outline of the leaf. Take it to be M
ii) Then count the number of squares that are more than half. Take it as N
iii) Next, Count the number of squares which are half of a whole square. Note it to be P.
iv) Finally, count the number of squares that are less than half. Let it be a Q.
v) Now the approximate area of the leaf can be calculated using the following formula.
Approximate area of the leaf = M+(3/4)N+(1/2)P+(1/4)
This formula can be used to calculate the area of any irregularly shaped plane figures.

\(\mathrm{M}=250 \mathrm{~g}=250 / 1000 \mathrm{~kg}=0.25 \mathrm{~kg} \)
\(\mathrm{~V}=1000 \mathrm{~cc}=\frac{1000}{1000000}=\frac{1}{1000} \mathrm{~m}^{3}\)
Density of liquid \(\mathrm{D}=\mathrm{M} / \mathrm{V}\)
\(\mathrm{M}=\frac{250}{1000} \mathrm{~kg} {~;} \mathrm{~V}=\frac{1}{1000} \mathrm{~m}^{3}\)

Density of liquid D = 250 kg/m³