Question

1. Define Law of Inertia. 2

2. Draw and label meristematic tissues. Also write their function 3

3. Why does desert cooler cool better on a hot, dry day? 2

4. Why does the naphthalene balls kept in stored clothes in our home disappear over

a period of time? 2

5. A bus decreases its speed from 80km/hr to 60km/hr in 5s. Find the acceleration of

the vehicle. 2

6. Define Second Law of Motion and derive its expression mathematically. 3

7. Classify plastids on the basis of colour and function.​

Answer 1

Answer:

( 1 ) Law of inertia, also called Newton's first law, postulate in physics that, if a body is at rest ýor moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a force.

( 2 ) There are some specialized cells in plants that are not differentiated and help in the growth of the plants. These cells in a plant can be young and have the ability to divide continuously. There is a special name for these cells, which are called the meristem cells. The tissue that these meristem cells form in plants is called as the meristematic tissue.

( 3 ) On a hot dry day, the amount of water vapour present in air is less. Thus, water present inside the desert cooler evaporates more, thereby cooling the surroundings more. That is why a desert cooler cools better on a hot dry day.

( 4 ) Naphthalene or mothballs kept between clothes disappear over a period of time because naphthalene balls undergo sublimation and form naphthalene vapours, which disappear into the air.

( 5 ) Initial speed   u=80 km/h=80×185=22.22 m/s

Final speed    v=60 km/h=60×185=16.67 m/s

Using   v=u+at

Or   16.67=22.22+α×5

⟹ a=−1.1 m/s2

( 6 ) Newton's second law of motion states that the acceleration of a system is directly proportional to and in the same direction as the net external force acting on the system, and inversely proportional to its mass. In equation form, Newton's second law of motion

( 7 ) Plastids are classified into three on basis of colour -

i) Leucoplast ( colourless )

ii) Chloroplast ( green colour )

iii) Chromoplast ( other than green )